Inspector Lewis has cracked his toughest case yet — discovering who he is.

Actor Kevin Whately, who plays the title character in the ITV drama, is the latest star to appear on BBC One’s Who Do You Think You Are? — a documentary series which features celebrities researching their genealogy.

Mr Whately’s journey starts in Newcastle and ends up in London, via Turkey, Syria and Palestine — and, interestingly, Oxford, where Lewis, and its predecessor Insector Morse, were filmed.

The 58-year-old, originally from Northumberland and who earlier this week revealed that the latest series of Lewis could be the last, said: “I come to Oxford every summer for two or three months to film Lewis, so I know Oxford very well.

“I am perceived, I think, as a working class Geordie, even though I am quite middle class. The Whatelys – my father’s lot – weren’t Geordies at all. They came from all over.

“In fact, for generations back they were all clergymen who studied in Oxford.”

The most illustrious of Mr Whately’s ancestors, and the one he knew most about, was his great-great-great-grandfather, Archbishop Richard Whately.

By the 1820s, Richard Whately had become one of Oxford’s most prominent academics.

In the programme, Mr Whately visited Oriel College to see a portrait of the archbishop.

He said his father had taken him to see the portrait when he was a boy, but he was too young to remember.

He said: “I feel like I have spent half my life in Oxford, but Richard Whately actually did.”

After researching his ancestry in Northumberland and Newcastle, and passing through Oxford, Mr Whately’s journey took him to London, where he learned of an ancestor born in the late 17th century who imported goods from the Middle East, made a fortune and bought a country house.

Mr Whately, himself a grandfather, said he was thrilled to have the chance to look back at his family’s history because he knew so little about it.

He said: “My dad was in the Navy and then died when I was in my teens so I didn’t get much chance to talk to him. I never knew my grandparents.”

At the end of the programme, the actor said it was surreal to know he was connected by blood to the people he had discovered in dusty archives and old photos.

The new series of Lewis begins on March 22.

tshepherd@oxfordmail.co.uk