Ambush in Leopard Street

Ambush in Leopard Street is a low budget 1962 British crime drama film directed by J. Henry Piperno. It stars James Kenney, Michael Brennan, and Bruce Seton.
Premise.
A small time crook, Harry, plans one last job before he retires, but things do not go quite according to plan. With his sidekick 'Nimmo', the plan is to ambush a truck containing £500,000 of diamonds in Leopard Street, but heavy security means recruiting a larger criminal gang than usual, and inexperienced newcomers threaten to derail Harry's scheme.