The programme was broadcast on BBC Two on Tuesday, 13 May, 2003 at 2100 BST.

This feature-length drama is set on Friday, 19 December, 2003.

In the film, Britain is facing a national crisis by the end of 2003; the country's transport infrastructure is unable to cope with the traffic volumes it faced on a daily basis.

Our roads are the most congested in Europe, our skies the busiest in the world and the rail network is lurching from disaster to disaster.

Total collapse of all these systems was just around the corner - the warning signs were there, but they were all ignored.

19 December, 2003 is the last Friday before Christmas; one of the busiest days for the UK's roads.

Operation Gridlock

In the drama, the day starts with the first of a series of 24-hour national rail strikes, following on from a fatal rail disaster at Waverley, Edinburgh. The strike pushed even more traffic on the roads.

By early afternoon the M25 is at a standstill following two accidents, and across the country minor incidents cause pockets of ever-growing gridlock from Scotland to the West Country.

By evening, hundreds of thousands of motorists are stranded in sub-zero temperatures and the police are forced to implement Operation Gridlock; a contingency plan intended solely for use in a humanitarian crisis.

The gridlock means passengers are unable to make their flights and hundreds of essential workers, including doctors, nurses, pilots and air traffic controllers, are unable to reach their place of work.

Understaffed and overloaded one air traffic controller makes a tiny mistake with devastating consequences.

At 22:28 the disaster many had predicted finally struck when a passenger jet collided with a Czech freight plane over Hounslow, killing all passengers and crew.