Kollisionen skete 08.09 frontalt mellem et Thames Train 3-vogns class 165, der var afgået fra London Paddington og det modkørende First Great Western High Speed Train (HST) (8 vogne med et diesellokomotiv i hver ende) på vej mod London Paddington. 31 personer omkom som følge af kollisionen, 227 blev alvorligt kvæstet (behandlet på hospitaler) og yderligere 296 blev lettere kvæstet.

Kollisionsstedet var ved Ladbroke Grove Junction ca. 4 km vest for London Paddington. Kollisionen skete stort set frontalt med en samlet hastighed på ca. 205 km/t.

Ved kollisionen blev den forreste vogn i Thames Train 0806 fra Paddington til Bedwyn, Wiltshire ¹⁾ blev fuldstændig knust og togets dieseloliebeholdning blev antændt og forårsagede flere brande i vragene, især i den forreste vogn i det modkørende tog. Vognen udbrændte fuldstændigt.

Som den umiddelbare årsag til ulykken blev det fastslået, at lokomotivføreren (Hodder) på Thames Train 0806 563 meter før kollisionen passerede signal SN109, mens dette viste rødt lys („stop“).

Den offentlige høring (undersøgelse), der over det næste år gennemførtes af Lord Cullen påviste imidlertid adskillige bagvedliggende faktorer, bla.:

• Thames Trains uddannelse af lokomotivførere (Hodder var blevet færdiguddannet 2 måneder før ulykken)
• Railtrack (ansvarlig for vedligeholdelse af spor og signaler), der ikke havde reageret tilstrækkeligt på at der havde været 8 signalforbikørsler af SN109 i de foregående 6 år hhv. ikke havde reageret på lokomotivførernes klager over dårlig synlighed på flere signaler - især SN109.
• Health and Safety Executive (Railway Inspectorate blev kritiseret for dets tilsynsprocedurer og
• Railtrack personale ved fjernstyringscentralen i Slough blev kritiseret for ikke at have sendt „nødstop“ pr. radio så snart det blev klart at SN109 blev passeret i „stop“. (De ventede at toget ville standse kort efter signalet, som det havde været tilfældet ved de tidligere signalforbikørsler ved SN109 - det er ikke klart om det radiosignal der blev sendt, blev modtaget før kollisionen 33 sekunder senere).

Lord Cullen

Jernbaneulykker

• [http://www.hse.gov.uk/railways/paddrail/lgri1.pdf Ladbroke Grove Rail Inquiry Part 1 Report] (3 MB pdf file) - Description of the accident and investigation
• [http://www.hse.gov.uk/railways/paddrail/lgri2.pdf Ladbroke Grove Rail Inquiry Part 2 Report] (1.3 MB pdf file) - Recommendations
• [http://www.hse.gov.uk/railways/paddrail/ladbroke.pdf Health and Safety Executive Report] (4.2 MB pdf file)
• [http://web.archive.org/web/20000312181821/http://stop.at/signal.109 Stop at Signal 109] - a website which lambasted Great Western Trains

The disaster occurred at the point where the main line from London to South Wales and the West of England switches from two lines in each direction, carrying fast and slow trains, to multiple lines signalled to allow trains to travel in either direction, in and out of the platforms of Paddington Station. The track layout had been modified in this way by British Rail in the early 1990s, but the line had subsequently been electrified to allow the new Heathrow Express service to operate from 1994, and the new overhead power lines obstructed the view of various signals. Signal SN109 had a particularly restricted view as there was a road bridge over the railway line a few hundred metres before the gantry on which SN109, together with four other signals, was mounted. The design of signal SN109 was non-standard, in that it was shaped like a reversed „L“, with the red lamp on the horizontal arm rather than near the top of the signal as is standard, and it is thought that this, together with the bright sun rising in the east behind the train and shining directly into the signal lenses may have misled the inexperienced Driver Hodder into thinking that the signal was showing a proceed aspect. The On-Train Data Recorder showed that he had reacted correctly to earlier caution signals.

This was the second major accident on the Great Western Main Line in just over two years, the other being the Southall rail crash of September 1997, just a few miles further west, and this severely damaged public confidence in the safety of Britain's privatised railway system.

On April 5 2004, Thames Trains was fined a record £2,000,000 for violations of health and safety law in connection with this accident.

The following people lost their lives in the Ladbroke Grove disaster: :Charlotte Andersen, 32, from Stillwater, OK, USA, resident in London, international products manager. :Derek Antonowitz, 25, from South Africa, resident in Willesden Green, London, computer consultant. :Anthony Beeton, 47, Civil Servant in the Northern Ireland Office. :Ola Bratlie, 26, from Gavdik, Norway, telecommunications engineer. :Roger Brown, 44, from east London, software engineer. :Jennifer Carmichael, 22, from Newbury, Berkshire, bar worker. :Brian Cooper, 52, from Hayes, Middlesex, (Driver of the HST) :Robert Cotton, 41, of Dursley, Gloucestershire, school caretaker and trade union official. :Sam Di Lieto, 24, from Bloomsbury, central London. :Shaun Donoghue, 45, of New Cross, London, statistician. :Neil Dowse, 39, from Forest Hill, London, sheet-metal worker. :Cyril Elliott, 41, from Beckenham, Kent, management consultant. :Fiona Grey, 33, from Dumbarton, IT consultant. :Juliet Groves, 27, from Shepherd's Bush, west London, accountant. :Sun Yoon Hah, 25, of London, barrister. :Michael Hodder, 31, from Reading, Berkshire, (Driver of the Thames Train) :Elaine Kellow, 24, of Paddington, IT worker. :Martin King, company director. :Antonio Lacovara, 24, from Hither Green, London, graphic designer. :Rasak Ladipo, 33, from Muswell Hill, London, computer expert. :Matthew Macaulay, 26, from New Zealand living in Clapham, S. London, information technician. :Delroy Manning, 39, from Lewisham, plasterer. :John Northcott, 24, from Leyton, east London, IT worker. :John Raisin, 61, from Painswick, Gloucestershire, recruitment consultant. :David Roberts, 35, of Swindon, Wiltshire. :Allan Stewart, 28, from Auckland, New Zealand, resident in Fulham, accountant. :Khawar Tauheed, 44, from Romford, Essex, microbiologist. :Muthulingam Thayaparan, 26, of Tooting, south London. :Andrew Thompson, 52, from Colchester, Essex. :Bryan Tompson, 61, from Cirencester, Gloucestershire, freelance engineer. :Simon Wood, 40, from Liss, Hampshire, charity project worker.

On 20 September 2005, [http://www.bbc.co.uk/pressoffice/pressreleases/stories/2002/06_june/20/railways.shtml Derailed], a 90-minute drama programme based on the events at Ladbroke Grove, was aired on BBC1. This dramatisation was heavily criticised in the railway press, with the editor of Rail magazine (Nigel Harris) describing it as a „trashy piece of subjective story-telling“ (issue 523). The programme itself stated that the chronology of actual events had been changed, and some scenes fabricated to „add clarity“.