A bit more detail.

In Britain, the rail network has been privatised, leading to frankly bollocks management of the rail infrastructure. The signals which could have prevented this travesty were blocked by trees, but Railtrack had done nothing.

At 8:06 AM, a Thames Trains service to Bedwyn passed a red signal on its approach to a junction. On the same track, a train operated by Last Awful Nowhere (also known as First Great Western) slows down to pull into Paddington. While traversing the junction onto the Bedwyn line, the FGW Class 43 Intercity plunges into the side of the Thames Turbo, hitting the front carriage almost head on.

Do realise that the Thames Turbo series (like its sister the Chiltern Turbo) is a diesel multiple unit (DMU) meaning that each carriage has an engine, full of nice, flammable DIESEL.

The front carriage of the Thames Turbo flies through the air and disintegrates as it goes. The Class 43 decouples, jumps the rails and catches fire (the Class 43 is a locomotive, meaning that diesel is only kept in the front carriage.). Diesel leaks and the 1st class carriage, plus the engine, catches on fire.

Remember what I said about all that diesel in DMUs? Well, both of the other Turbo carriages have jumped off the rails and fallen over too. And they're burning.

AT MANY THOUSANDS OF DEGREES.

The second and third MK3 TS carriages on the FGW/LAN train fall on their side, the second catches fire. 30 died, many others were injured. The fire burnt for days.

This shambles was exacerbated by the fact that in the FGW train, the doors had automatic locking, and the hammers to break the windows were hard to find. In the Thames Turbo, the hammers did not exist (Chiltern have hammers in their trains, but also have one of the best safety records, so the hammers are rather pointless). Also, the TT driver had only just started work and had not been fully trained.

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The aftermath? Thames Trains and Railtrack were prosecuted. Thames changed its logo (the pitchfork rising from water had connotations of hell, this needs no further explanation) to a rather more friendly symbol, and First was absolved of all responsibility as they played no active part in the crash (they followed the signals OK while Thames did not). And the railway improvement crusade now have another metaphorical bullet in their gun, with which to threaten the government.

See also Potters Bar.