The Unstoppable Man

The Unstoppable Man is a 1960 British crime drama film directed by Terry Bishop and starring Cameron Mitchell, Harry H. Corbett, Marius Goring and Lois Maxwell.
Plot.
A gang of criminals kidnaps the son of James Kennedy, who is an American executive of a London-based chemical company.
Kennedy ignores the advice of Inspector Hazelrigg of Scotland Yard to try a plan of his own. He doubles the ransom amount, expecting the thieves to have a falling-out over how to divide it. One is indeed killed, and evidence at the crime scene leads Kennedy to a home in Hampstead where the mastermind, Feist, is keeping Kennedy's son.
Hazelrigg comes along, but agrees to give Kennedy a few minutes to enter the house alone. Armed with a flamethrower, Kennedy is able to take his son to safety while the police close in on Feist.
Critical reception.
In a contemporary review, "The Monthly Film Bulletin" praised the film's "sharply drawn characters", "authentic backgrounds" and "slick and resourceful" direction; and more recently, "Mystery File" wrote, "While there’s nothing in "The Unstoppable Man" that’s exceptional, that doesn’t mean that it isn’t a good — make that a very good — crime film. Running at around seventy minutes, it’s economical both on plot and the viewer’s time. But what it lacks in originality, it makes up for in atmosphere and an early 1960s jazz-influenced soundtrack that works very well."