The Green Finger (1946)

This is the first film based on Francis Durbridge's long-running BBC Radio serial. A gang has been executing a daring series of smash and grab robberies. A policeman on the case appears to commit suicide, but crime novelist and amateur sleuth, Paul Temple, suspects foul play. With the help of the victim's sister, reporter Louise Harvey (who uses the pseudonym "Steve Trent"), Paul sets about tracking down the notorious diamond robbers...