Ruth Wilson plays her own grandmother in, Mrs Wilson

In 1963 Alison Wilson is a neat, happy woman with a job in an office typing pool, two fine children and a husband, Alec, who’s a successful writer at home at his desk in comfortable suburbia.

But Alison’s world implodes when Alec (Iain Glen) dies suddenly and a woman knocks on her door to make an extraordinary claim. Ruth Wilson is tremendous as older Alison and, in flashbacks, as young Alison, a dewy-eyed country girl who leaves Cumberland for London and the excitement of working for the secret service during the Second World War.

It’s here she meets the much older, very charming, dashing and married Major Alec Wilson. But by the end of the episode, Alison isn’t sure who her husband really was…

Watch the trailer here.

Watch on Tuesday 27th November on BBC One at 9pm.