Breach is slow, but never ponderous, and not at all like your average spy thriller. It has less obvious thrills and more depth.

A sombre game of cat-and-mouse. What it lacks in genuine tension it amply compensates in the understated performances of the two leads.

Intriguing and intelligent, Breach may be too understated for its own good.

It's worth remembering this astonishing bit of US history, where a young investigator took down his boss, an FBI agent named Robert Hanssen. These two men are caught between truth and lies and only one of them likes the lie.