He plans to steal a monthly shipment of gold from the London to Folkestone train which is meant as payment for British troops fighting in the Crimean War.

Pierce's mistress Miriam and his chauffeur Barlow join the plot, and a train guard, Burgess, is bribed into participation.

Miriam reluctantly poses as "Madame Lucienne", a courtesan in an exclusive bordello, meets with Fowler and asks him to undress, forcing him to remove the key worn round his neck.

Pierce then stages a phony police raid to rescue Miriam, forcing Fowler to flee to avoid a scandal.

After a daytime diversionary tactic with a child pickpocket fails because Agar cannot wax them in the time available, Pierce decides to "crack the crib" at night.

Because Clean Willy is incarcerated at Newgate Prison, Pierce and Agar first have to arrange for him to break out, using a public execution as a distraction.

However, soot from the engine's smoke has stained Pierce's skin and clothes, and he is forced to borrow Agar's suit, which is much too small for him.

[7] Sean Connery performed most of his own stunts in the film, including the extended sequence on top of the moving train.

[8] The train was composed of J-15 class 0-6-0 No 184 of 1880, with its wheels and side rods covered and roof removed, leaving only spectacle plate for protection to give it a look more akin to the 1850s, and coaches that were made for the film from modern railway flat wagons.

Connery wore soft rubber soled shoes and the roofs of the carriages were covered with a sandy, gritty surface.

Connery actually slipped and nearly fell off the train during one jump between two carriages, and had difficulty keeping his eyes free of smoke and cinders from the locomotive.

The robbery was a year in the planning and involved making sets of duplicate keys from wax impressions for the locks on the safes, and bribing the train's guard, a man called Burgess.

In his screenplay Crichton based his character "Clean Willy" Williams on another real-life character from Chesney's book, a housebreaker named Williams (or Whitehead) who, sentenced to death in Newgate Prison, escaped from prison by climbing the 15-metre (50-ft.) tall sheer granite walls, squeezing through the revolving iron spikes at the top, and climbing over the inward projecting sharp spikes above them before making his escape over the roofs.

The scenes on the moving train were filmed on the Mullingar to Athlone railway line (now closed) at Castletown Geoghegan Station.

"[19] Roger Ebert of the Chicago Sun-Times gave the film three stars out of four and singled out Connery, writing that the actor "is one of the best light comedians in the movies, and has been ever since those long-ago days when he was James Bond.

"[20] Vincent Canby of The New York Times praised director Crichton's "amplitude...in this visually dazzling period piece,"[21] and that "the climactic heist of the gold, with Mr. Connery climbing atop the moving railroad cars, ducking under bridges just before a possible decapitation, is marvelous action footage that manages to be very funny as it takes your breath away.

"[21] Gene Siskel of the Chicago Tribune gave the film two-and-a-half stars out of four and wrote that it "takes too much time to get to the robbery itself."

He found very little suspense in the first half of the movie "because we know that Connery's gang must get the keys or we won't be able to see the big robbery of the film's title.