Considered the most beautiful debutante of the 1930s, heiress Margaret Sweeny (Claire Foy) is in the midst of a divorce when she meets the dashing - and married - Ian Campbell, future Duke of Argyll (Paul Bettany).

What begins as sexual chemistry evolves into something more serious when Margaret not only begins to fall in love with Ian - by now the Duke - but also with his crumbling ancestral seat, Inveraray.

With the perfect man - and perfect castle - in her sights, Margaret persuades her doting father to help her pay for the castle’s restoration, whilst Ian secures a divorce from his humiliated wife.

The pair marry, but the honeymoon phase soon sours. Ian is consumed by his plan to raise a legendary treasure from Tobermory Bay, and while Margaret is able to restore the castle to its former glory - at huge expense – Ian’s temper is often more than she can handle.

When she realises that her claim to the castle might not be as secure as she once thought, she starts a series of events that will change not only her life and the lives of those around her, but also the perception of the British aristocracy forever.

A Very British Scandal is made by Blueprint Pictures for BBC One and BBC iPlayer.