This is a 1960 British crime drama directed by Basil Dearden, based on the 1958 novel of the same name by John Boland.
Although the robbery plan seems quite interesting, the plot appears ill-contrived.
A small boy outside the bank is collecting car's plate numbers.
This is such a cheap trick that anybody could guess that this would solve the crime in the end.
The robbery members show little enthusiasm at first but Colonel Hyde reveals each person's misdemeanors.
I don't think that these ill-motivated men could accomplish such an extraordinary heist in the first place.
In any case, you would need a willing suspension of disbelief.