One of those charming English movies of a bygone age, The Titfield Thunderbolt is a classic Ealing Comedy, of small-town folk standing up for what's right. Set not long after the Nationalisation of the UK's railway system, the rural village of Titfield relies heavily on the local branchline for it's survival. Early on, British Railways decides to close the line, which would leave the village in desperate straits.

The local parish vicar, the Reverend Sam Weech, a lifelong trainspotter, conspires with Gordon Chesterford, the local Squire, to persuade local businessman and drinker Walter Valentine to finance them with ten-thousand pounds to buy the branchline. The move is bitterly opposed by Alec Pearce and Vernon Crump, who stand to profit with a replacement bus service, but a passionate plea by Chesterford at the court of enquiry persuades the government offical to grant them a temporary approval to operate for a month, before a Railways Inspector comes to give the final say in the granting of a Light Railway Order (LRO).

Despite Crump and Pearce's best efforts, which include sabotaging a water tower by shooting holes in it, the villagers become a national sensation, and look set to get their LRO and save their railway. The night before the inspection, however, they enlist the aid of local steam-roller driver Harry Hawkins, who has his own grudge against the scheme, to tow the engine and coach down a grade, to where the two busmen have removed a rail, which causes the train to be wrecked.

Despairing, Weech returns to the vicarage, and falls asleep by his fireplace, where he has a dream about the first engine to run the branchline; the titular "Thunderbolt". He rallies the villagers, and through the night requisition the venerable steam locomotive.

The Inspection arrives, and despite a few hiccups along the way, the LRO is approved, and the line is saved.