Adapted from Ben Macintyre’s book, the screenplay is a brisk and jolly affair, taking gamey delight in comparing the art of espionage to the fibs of professional storytellers.

It is quite a moving story. Colin Firth [and the ensemble] do really solid, good work here.

It’s exactly the kind of well-rounded, satisfying movie which works on all levels but doesn’t particularly dazzle on any – and it doesn’t have to because it does what it needs to do.

Wartime London has been recreated in painstaking fashion, and the performances are heartfelt and strong.