Signals Unseen: The 1952 Harrow and Wealdstone (England) Train Collision

Max S
15 min readJan 21, 2024


Harrow is a suburb of 149246 people (as of 2011), which stands today as the “London Borough of Harrow”, losing the status of a fully independent city in 1965. It is located on the northwestern edge of the English capital, 18km/11mi from central London and 33km/20.5mi south of Luton (both measurements in linear distance).

The location of Harrow in Europe.

Harrow was served by the Harrow & Wealdstone station, which opened as “Harrow station” in 1840 before being renamed to its current name in 1897 as the neighboring district of Wealdstone grew and became equally important to the station’s traffic. The station lies on the West Coast Main Line (WCML), a 642 km/399mi double- to six-tracked main line connecting Glasgow (Scotland) with London (England) as one of the UK’s main rail corridors.

Harrow & Wealdstone station held six tracks at the time of the accident, split into three pairs. From east to west those were slow lines for local trains and shunting, the fast lines meant for express trains on the WCML, and the DC Electric Line, a commuter rail line already electrified back in 1912. Each pair, as usual for the UK’s main lines, was split into an “Up” and “Down” line, “Up” refering to the southbound track towards London and “Down” to the northbound track towards Scotland.

The site of the accident seen from above today. The local train and the Night Express were travelling southbound (towards the bottom of the image), the Euston Express was coming the other way.

The Trains Involved

The 7:31am local passenger train from Tring to London’s Euston station (referred to as the local train in this article) was a nine-car passenger train travelling on the Up Slow Line, which was switching over to the Up Fast Line ahead of Harrow & Wealdstone and stopped at the station on that track. It consisted of 9 passenger cars, using newer all-steel cars towards the front with two wood-bodied cars at the back. It was hauled by LMS (London, Midland and Scottish Railway) locomotive number 42389, an LMS Fowler 2–6–4T tank engine. The Fowler 2-6-4T was a passenger steam locomotive introduced in 1927, running on three driven axles along with a leading and two trailing axles (hence the numbers in the name, refering to the wheel-distribution). Each Fowler 2–6–4 measured 14.40m/47ft in length at a weight of 87.6 metric tons, excluding the 3.6 metric tons of coal and 9100l/2400 US-gallons of water it carried if fully loaded. The type was known for being unexpectedly fast, being clocked at speeds beyond 130kph/80mph. The local train was unusually crowded on the day of the accident, carrying around 800 passengers as the following train on the same connection had been cancelled.

LMS #42389, the locomotive pulling the Tring train involved in the accident, photographed in 1959 running “bunker-first” (in reverse) as it did during the accident.

The Night Express was an express passenger service from Perth (Scotland) to London’s Euston station on the Up fast line, consisting of 11 four-axle express passenger cars pulled by LMS locomotive number 46242, christened “City of Glasgow”. The locomotive was a “Coronation Class”-unit, a class of heavy steam locomotives for express passenger services introduced in 1937. Each Coronation Class locomotive measures 22.5m/74ft in length including their four-axle pulled tender and had an empty weight of 110 metric tons plus the 57 metric ton tender. The type could reach a top speed of 183.4kph/114mph, which briefly earned it the speed record for British locomotives. The Night Express was lightly occupied on the day of the accident, carrying just 85 passengers.

LMS #46242 “City of Glasgow”, the locomotive pulling the Night Express, photographed with the British Royal Train at an unknown point in time. The bottom-center headlight was only installed when pulling that train.

Lastly, there was the 8:00am passenger express service running on the Down fast line from London’s Euston station to Liverpool and Manchester (referred to as the Euston Express in this article). It consisted of 15 four-axle express passenger cars carrying approximately 200 passengers pulled by two locomotives. Leading the train was LMS #45637 “Windward Islands, assisting LMS #46202 “Princess Anne”. The #45637 was a “Jubilee Class” steam locomotive, a passenger train locomotive introduced in 1934. The type ran on three driven and two leading axles and had a total length of 19.73m/65ft at an empty weight of 136 metric tons including its pulled tender.

LMS #45637 “Windward Islands”, the leading of the two locomotives pulling the Euston Express, photographed at an unknown time before the accident.

The second locomotive pulling the Euston Express was LMS #46202, christened “Princess Anne”, a Princess Royal Class express passenger train steam locomotive. The Princess Royal Class was introduced in 1933, running three driven axles with two leading and one trailing axle. The “Princess Anne” specifically had been one of the class’ three prototypes, being built as a unique experimental steam turbine locomotive nicknamed the Turbomotive. It was rebuilt in the class’ standard configuration in August 1952 after it had been in storage for three years because of a turbine failure. Each Princess Royal Class locomotive measures 22.66m/74ft in length at an empty weight of 162 metric tons including the tender.

The freshly rebuilt #46202 “Princess Anne”, the second locomotive pulling the Euston Express, photographed while being cleaned about a month before the accident. It short post-rebuild service life makes photos in that configuration rare.

The Accident

The local train pulls into Harrow and Wealdstone station at 8:17am on the 8th of October 1952, running 7 minutes behind schedule because of fog along its way demanding lower speeds. It had traveled most of the way from Tring on the Up slow line before moving over to the Up fast line right before Harrow and Wealdstone station as the Up slow line south of the station was required for the shuttling of empty train cars. Various passengers enter and leave the stopped train from and to platform 4 for approximately 1.5 Minutes before the doors are closed as the train prepares to depart. It would never get to that, though, as the Night Express comes racing into the station at 8:19am, crashing into the back of the stopped local train at approximately 90kph/56mph. The impact crushes the wooden bodies of the rear two passenger cars, forcing their remains into the rearmost steel-bodied passenger car which itself suffers heavy compression damage. The three cars are compressed to the length of little more than one passenger car as the whole train is shoved forwards by 18m/59ft before its passenger cars proceed to crash into and derail around their locomotive.

Most of the wreckage is spread across the platform and Up fast line, but some has spilled onto the Down fast line, which proves fatal when the Euston Express plows into the wreckage blocking its track before it had come to a rest. The impact separates the locomotive of the Euston Express from its train, with the leading passenger cars being launched upwards, climbing over the wreckage until they strike the pedestrian overpass, bringing part of it down on the still moving wreckage. 112 people die in the disaster and 340 are injured, making it Britain’s second-worst rail accident in history.


The first responders arrived at the site by 8:22am, being faced with a sprawling wreckage that covered most of the station’s width at a considerable distance. Train cars, pieces of them and remains of station infrastructure had been strewn all over the place, centered around a chaotic pile 41m/134.5ft long, 16m/52ft wide and 5.5m/18ft high, completely hiding the Night Express’ locomotive. Elsewhere among the debris a whole steam locomotive had ended up on it’s side on the southernmost platform. That locomotive was the Princess Anne, which had been dragged along by the “Windward Islands until it broke free from the disintegrating locomotive. The Princess Anne’s crew actually survived, climbing from the remains of their severely damaged, almost-new locomotive after the accident. The crew of the oncoming Night Express, which they had struck just about head-on by coincidence, wasn’t as lucky, dying when their locomotive was driven back into its own tender. The timing of the tragedy had been so close, it’s assumed that the already crashed Night Express hadn’t even come to a rest yet when the Euston Express ran into it.

LMS #46202 “Princess Anne” sitting in the wreckage, having shaved most fittings off its outside along the way.

A group of soldiers from the US Air Force had been aboard one of the trains involved (which one isn’t clear) and found themselves among the survivors. They alerted their medical teams at RAF South Ruislip, an air force base just 8km/5mi away, who sent emergency response teams usually intended for medical treatment in battlefield scenarios. 102 people died in the initial collisions, another 10 would later succumb to their injuries. Among the dead were 14 of “unclear origin”, it’s assumed that they had been waiting at the station when the derailed Euston Express came barreling across the platform. The last ambulance left with a survivor at 12:15pm, with the search for further survivors continuing until 1:30am the following morning without any successes.

A photo from the report showing the center of the wreckage with the overpass’ steel girder sitting on the train cars (annotations from the report moved into the photo by me).

The Ministry of Transport opened an investigation into the accident right away and appointed Lieutenant Colonel Wilson, a senior member of the Railway Inspectorate (the British organization in charge of investigating rail accidents), to lead it. The investigation figured that the signaling system on the line had been working as intended, with the local train being protected by three different signals if approached from the north. Going northbound from the local train’s position there was a semaphore signal referred to as the “Up Fast Inner Home” 170m/186yd up the line from the back of the local train, followed by another semaphore signal (“Up Fast Outer Home”) another 400m/437yd back from that one. A British semaphore signal consisted of a rectangular board painted either yellow with a black stripe or red with a white stripe, which would be kept horizontal to signal “stop” or angled downwards to signal “clear”, usually accompanied by a red or green lens at the post-side of the board. The wires moving the board were fitted with a heavy counterweight, so a failure of the wire would automatically set the signal to “stop”.

A pair of surviving British semaphore-signals photographed in 2012, both displaying “stop”.

Heading further north there was a third signal protecting the local train, a so-called “color distant signal” (pre-signal, in simplified terms) 1348m/0.84mi up the line from the Up Fast Outer Home. These signals couldn’t display a stop-order, they were linked to the following signal and either showed green (“proceed”) if the following signal was green or yellow (“slow”/”expect stop”) if the following signal was red. The distance to the Up Fast Outer Home was the specific braking-distance of a heavy express train at the section’s top speed of 120kph/75mph, meaning a train passing the pre-signal at yellow would have sufficient space to stop for the red signal it was about to encounter. All three signals showed the intended message when they were inspected after the collision. The investigation dismissed the possibility of a signalman setting the signals to the intended settings after the crash occurred, finding no reason to accuse the signal box crew of such a thing. Some survivors from the Night Express recalled no deceleration until right before the collision, when a very strong brake application could be felt just a second before impact. This, the investigation concluded, was likely an emergency stop being triggered after the train blew through the third signal telling it to slow down/stop.

Local trains actually had priority over long-distance express services in the area around Harrow and Wealdstone station, especially when delays came into play, so the driver of the Night Express should have expected a stop-order being communicated. The driver is referred to in the report as a “methodical young man” who was in good health, with no evidence of a medial emergency incapacitating him ahead of the accident. Since the crew of the Night Express perished in the crash they couldn’t be asked about their actions before the accident, making much of the investigation educated guesswork.

The driver’s cab and tender of the Night Express after being pulled apart during recovery, having been jammed together during the accident.

The report rejects the theory of the Night Express’ driver accidentally looking at the signals for the neighboring Electric Line, saying that a driver with the experience and route knowledge held by the Night Express’ driver wouldn’t make such a basic mistake. Furthermore, it’s deemed unlikely that the sun blinded the train crew. It’s noted that the sun was sitting low at just 9° above the horizon, but was at an angle of 17.5° to the left of the straight track, with some lingering fog further “softening” its glare.

Sight distances at the site were measured at 180–270m/590–885ft, with the report noting that the fog was clearing as they were measuring, while witnesses who saw the Night Express pass the Up Fast Distant signal out in the countryside estimated just 46–91m/151–299ft, a distance covered in about four seconds at the speed of the express. Running out of concrete evidence, the report speculates the following:

In these circumstances I can only suggest that [The Night Express’ driver] must have relaxed his concentration on the signals for some unexplained reason, which may have been quite trivial, at any rate during the few seconds for which the Distant signal could have been seen from the engine at the speed he was running in a deceptive patch of denser fog.

Remains of several train cars, wrapped around remains of the collapsed overpass.

This lapse of attention, which didn’t need to have lasted more than a few seconds, would have been enough for the driver to lose track of the train’s location, leading to him possibly expecting the passed signal to show up ahead of him. He also may have been focused on spotting the light signal (which he had passed without noticing), which would have had him looking much lower than the height at which the semaphore-signals were mounted. It’s unknown if the brake application felt by passengers was triggered when he saw the final signal or only once he saw the stopped local train ahead, but either way it was too late to slow the train down, much less stop. His fireman, standing on the other side of the cab, wasn’t concerned with the signals after passing one mounted on his side of the tracks much earlier along the journey, so he cannot be blamed for likely having been focused on running the locomotive rather than looking out ahead.

An overview of the main wreckage, showing debris spread across all tracks.

The official report was published in June 1953, blaming the crash on the Night Express’ driver disregarding at least one signal order. Why exactly the driver of the Night Express didn’t slow down when he passed either of the first two signals could never be determined. There were no direct recommendations on how to “fix” the issue which caused the accident, with the report explaining:

The Rules and Regulations for train working in fog have proved adequate in practice with the aid of the professional skill and care which is displayed by engine drivers throughout the country on the vast majority of occasions. The way to guard against the exceptional case of human failure of the kind which occurred at Harrow does not lie in making the regulations more restrictive, with consequent adverse effect on traffic movement, but in reinforcing the vigilance of drivers by apparatus which provides a positive link between the wayside signals and the footplate [the Footplate is a term for the driver’s cab, specifically its floor].

Rescuers scale the towering wreckage as smoke seems to escape from one of the wrecked locomotives.

The report suggests implementation of a system that would warn drivers if they passed a yellow pre-signal or a main signal ordering a stop, noting that such a system would have prevented ten percent of the accidents (and 28% of the suffered fatalities) suffered by British railways in the previous 41 years, which comes out to 399 lives including those at Harrow and Wealdstone. The system, later named simply AWS (“Automatic Warning System”) was already in development at that time. It would warn a driver if they approached a signal at yellow or read, and could trigger an automatic stop if the driver didn’t acknowledge the warning. The report came out shortly after a five year deadline had been set to install the system on 2144km/1332mi of track for field introduction/practice testing.

Lieutenant Colonel Wilson closes the report with a statement on the possible unintended message behind suggesting widespread use of AWS, intending not to seem like he wanted people to distrust train drivers by writing:

The very occasional failures which have occurred give no grounds for loss of confidence in British railway engine drivers as a whole, and there is no reason to believe that the problem has become more urgent in the last few years, notwithstanding the exceptionally tragic results of one such failure at Harrow. All, however, are agreed that drivers should be given their share of technical aids to safe working, and I consider that at this late stage there should be no reservations on the rate of progress once the apparatus has been approved.

The remains of a train car sit in the wreckage, having been shaved off and moved beyond their frame and wheels.

The accident ended up accelerating the introduction of AWS, overcoming criticism about its usefulness compared to installing more signals. One third of the British rail infrastructure had the system installed and operational by 1977. The system uses a permanent and an electromagnet mounted between the rails to create magnetic fields of certain frequencies which are then picked up by a sensor on the train. The magnetic field from the permanent magnet triggers a warning in the driver’s cab in the form of a horn and a visual indicator. It always has the same polarity and can’t fail, meaning a power-outage will not keep it from producing a warning. The electromagnet paired with the permanent magnet can be powered on to create a second magnetic field of opposite polarity. The train, when picking up both fields, would then give an “all clear” indication to the driver, accompanied by a bell sound and requiring no action by the driver. If the driver received a warning (electromagnet powered off), however, they had 2–3 seconds to press an “acknowledge”-button, preventing an application of the brakes.

The track-mounted magnet pack used for AWS.

Another lesson learned in the accident was the safety of (at the time) modern train cars, with only eight people dying in the severely damaged forward seven cars of the Euston Express. These cars had been built to the newest standard at the time, featuring all-steel construction with their bodies welded to the frame rather than bolted and a new type of coupling which could endure higher forces before separating. All-steel welded passenger cars are the standard by now (21st century), and most if not all modern train cars feature energy-absorbing structures built into their coupler-area to reduce forces inflicted on passengers in an accident.

The locomotive of the local train got away from the carnage undamaged and remained in service until being retired in 1963. Both locomotives from the Euston Express were damaged beyond repair and written off, marking the end of the “Princess Anne” so soon after its rebuild. The name-plates from the exterior of the “Princess Anne” and the “Windward Islands” were retrieved from the wreckage and acquired by the Doncaster Grammar School, where they remain today.

In contrast, “City of Glasgow”, the locomotive which had been pulling the Night Express, was dragged from the wreckage and rebuilt, serving until 1963. It was retired along with the rest of its type as they were too tall for electrified lines, putting their steel chimneys too close to the high voltage wires. Three locomotives of the type remain as of 2023, with one in operational condition.

The “City of Glasgow” after being recovered and placed on a siding. Despite the severe damage it went on to be repaired and served another 11 years.

Criticism of the station’s layout and the habit of having the local train stop at the platform on the Fast tracks led to changes in the station layout in 1962, moving the points and making it the norm to stop local trains on their own tracks rather than having them switch over.

A memorial plaque on the main entrance to the station was unveiled in 2002 on the accident’s 50th anniversary. The white marble plaque is engraved with golden letters reading simply:


A crowd gathers for the unveiling of the memorial (located below the station sign) in 2002. It seems like a rather sparse memorial for the size of the accident it relates to.


I have chosen to stay off Medium’s monetization offers to keep these stories as accessible as possible, but you can support me with a small tip via “Buy me a coffee” if you feel like it.


A kind reader is posting the installments on reddit for me, I cannot interact with you there but I will read the feedback and corrections. You can find the post right here.



Max S

Train crash reports and analysis, published weekly.