No fault was found with the train, and the inquiry by the Department of the Environment concluded that the accident was caused by the actions of Leslie Newson, the 56-year-old driver.

With no services running into the adjoining platform to produce the piston effect pushing air into the station, ventilation was poor and temperatures in the tunnel rose to over 49 °C (120 °F).

[1] The first line opened in 1863 and by 1975 the network contained 250 miles (400 km) of route track; that year three million people used the service each day.

[4] At the end of platform 9 in 1975 was a red warning light atop a post, situated in front of a 61-centimetre-high (2 ft) sand drag placed to stop overrunning trains.

Robert Harris, the 18-year-old guard who had started working for London Underground in August 1974, was late and joined the train when it returned to Moorgate at 6:53 am; a driver waiting to go on duty took his place until his arrival.

Newson and Harris made three further return trips before the train undertook its final journey from Drayton Park at 8:38 am, thirty seconds late.

A passenger waiting to take the return journey stated that Newson appeared "to be staring straight ahead and to be somewhat larger than life".

[19] Witnesses standing on the platform saw Newson sitting upright and facing forward, his uniform neat and still wearing his hat; his hands appeared to be on the train's controls as far as they could tell.

[20] The brakes were not applied and the dead man's handle was still depressed when the train entered the overrun tunnel, throwing up sand from the drag;[c] when the driver's cab crashed into the hydraulic buffer, the carriage was separated from its bogie and the coachwork was forced into the end wall and the roof.

[23] Javier Gonzalez, a passenger who was travelling in the front carriage, described the moment the train crashed: Just above my newspaper I saw a lady sitting opposite me and then the lights went out.

[28] At around the same time the City of London Police alerted nearby St Bartholomew's Hospital (Barts) that "a tube train had hit the buffers" at Moorgate, but there was no indication at that stage of the seriousness of the crash.

After assessing the situation, Dean realised that he did not have enough painkillers with him, or in BP stores, so he went to the Moorgate branch of Boots where the pharmacist gave him the shop's entire supply of morphine and pethidine.

[32] One of the doctors from Barts later described the scene: The front carriage was an indescribable tangle of twisted metal and in it the living and the dead were heaped together, intertwined among themselves and the wreckage.

It was impossible to estimate the number [of casualties] involved with any degree of accuracy because the lighting was poor, the victims were all tangled together, and everything was covered with a thick layer of black dust.

[34] By 9:30 am Moorgate and many of the surrounding roads had been cordoned off to allow space for the co-ordination teams above ground to manage the flow of vehicles—particularly for ambulances taking casualties to hospitals.

[35] To make a clear passage through the wreckage for equipment, the emergency services and injured commuters, a circular route was organised through the carriages.

Firefighters cut holes in parts of the structure, including in the floors and ceilings of the carriages through which it was possible to move, even if it meant crawling through some areas.

[41] A large electric fan was placed at the top of the escalators in an attempt to remedy the situation, but soot and dirt was disturbed and little draught was created; the machine was soon turned off.

[43] The Fire Brigade worked for several hours to release Benton, but it became apparent that Liles needed to be removed first, which could only be done by amputating her left foot.

Shouts were made for any people trapped to respond; there were no responses and the site medical officer declared that all the remaining bodies in the wreckage were dead.

[55][56] Hafter reported his examination about Newson to the subsequent inquiry: His left hand was close to, but not actually on the driver's brake handle and his right arm was hanging down to the right of the main controller.

[63] McNaughton's inquiry began on 13 March and was paused after a day and a half; during that time it was established that the mechanics of the train were in working order and that there were no known problems with Newson's health, although the results of pathological tests were still awaited.

McNaughton said he was perplexed as to the causes of the crash, but that he would proceed with the next part of his inquiry, which was to undertake further enquiries and to consider measures so the accident could not be repeated.

[65] David Paul, the coroner, was unhappy that a government inquiry had already begun, as evidence was in the public domain, and could affect the inquest's jury.

[73] McNaughton observed that because of Harris's lack of experience, he could not have taken any action to stop the accident from happening, although he thought the young man "displayed himself as idle and undisciplined".

[80] Medical evidence presented to the inquiry raised the possibility that the driver had been affected by conditions such as transient global amnesia or akinesis with mutism, where the brain continues to function and the individual remains aware, although not being able to move physically.

There was no evidence to indicate either condition: to positively diagnose akinesis with mutism would depend on a microscopic examination of the brain, which was not possible because of decomposition, and transient global amnesia leaves no traces.

[86] Since the death of a driver in 1971, when an empty stock train crashed into buffers in a tunnel siding near Tooting Broadway, London Underground had been introducing speed controls at such locations.

[91][page needed] In the south-west corner of Finsbury Square, 410 metres (450 yd) north of Moorgate station, a memorial lists those who died.

[92][93] On 28 February 2014 a memorial plaque was unveiled by Fiona Woolf, the Lord Mayor of London, on the side of the station building, in Moor Place.