Shadow Run (1998)

"A hardened gangster plans to steal £100 million in 20 minutes... and take full advantage of the shadow run. All he has to fear is his partner."

Haskell is assigned a job by his boss, the aristocratic Landon-Higgins, to highjack a high security van in broad daylight while it's in the shadow run (out of radio contact with the main security firm). He assembles a team to carry out the heist, but things don't go according to plan and Haskell begins to think his boss might be double crossing him. Add to this, a teenage boarding school pupil has already witnessed some of the meetings of the team and Haskell's in real trouble.