IT'S Friday lunchtime and in the cosy library of a London hotel, Bill Nighy is talking murder mysteries and his Glasgow roots.

The actor, who starred in Love Actually, Harry Potter and Pirates of the Caribbean, will return to our screens in a new three-part BBC adaptation of Agatha Christie's Ordeal by Innocence on Easter Sunday.

Bill, 68, plays Leo Argyll in the suspense-fuelled storyline with Anna Chancellor as his wife Rachel, a wealthy philanthropist and mother to five adopted children.

Set in the 1950s, the action unfolds at the family estate Sunny Point – shot on location at Ardgowan Estate near Inverkip – and, in true Agatha Christie style, there is soon a murder.

The glittering cast for the big-budget drama includes Morven Christie, Eleanor Tomlinson, Matthew Goode and Alice Eve, alongside Crystal Clarke and Ella Purnell.

"It is a very strange household because he and his wife have adopted five children, all from what you would call troubled pasts," says Bill. "There are very complex and complicated relationships within the family – and within the household generally.

"Leo is an amateur Egyptologist and he is a man of his time. He is impeccable with the children and very conscientious as a stepfather. It is a tough ship to handle because, as I say, there are so many different forces going in so many different directions."

Ordeal by Innocence was due to be shown on Boxing Day last year, but swiftly shelved after Ed Westwick, who played Mickey Argyll, faced allegations of rape and sexual assault in the US dating back several years, which the actor has strongly denied.

Christian Cooke replaced Westwick in the role and large sections were reshot in January.

None of that had yet unfolded when I meet Bill. He talks warmly about filming in Scotland. "I loved it. I'm not just saying this because you are from there," he says. "My mother came from Glasgow. She left when she was 15. She came from the Gorbals, the classic big Irish Catholic family.

"They left to find work when she was 15, but she always spoke of Glasgow with great longing. She was born there, but both her parents were Irish. She did go back a few times. I never went with her, although my sister went once.

"It was very nice and did have meaning for me to spend proper time in Glasgow. I was there about four or five weeks. I felt very comfortable and happy there."

While he didn't get a chance to visit the Gorbals, Bill did spend time at the Tenement House museum. "Which was very interesting," he says. "It is actually quite a posh tenement, whereas my mum would have grown up in what they called 'a single-end'.

"Seeing the middle-class tenement – because it had three rooms – I thought: 'Blimey, this is a bit posh'. They had those alcove beds which open out. In my mum's family, there were five girls and five boys, so she would sleep with the girls and the boys would sleep together."

It's perhaps credit to his mother's roots that Surrey-born Bill purveyed a rather decent Scottish accent as gruff-voiced Davy Jones in the Pirates of the Caribbean films.

"I never thought of my mum as Scottish, then I would hear her on the phone" – he demonstrates an impressive Glaswegian accent – "and I would think: 'Oh, my mum is Scottish …' It was always a surprise because she very rarely used the phone, she was that generation."

Based in the West End during filming, Bill even popped his head into Hyndland Gala Day one Saturday afternoon and posed for photographs with delighted fans.

"Hyndland Street and Hyndland Road was my patch because I was staying at Hotel du Vin at One Devonshire Gardens," he says. "I would walk down to Epicures of Hyndland. The Hyndland Bookshop is really good. I love independent bookshops. I bought loads of books there.

"The ones I didn't get around to reading – and I'm always doing this – I would hide in the bottom drawers of my hotel room. You hope that someone will come in afterwards and go: 'Oh, look! There's a book.' So, I hid a few."

I like his style. In some hotels, the only choice of reading material is a Bible. "Exactly," nods Bill. "Now they've got a bit of James Baldwin. I discovered him very late in life. Two of the books I read while I was there were James Baldwin."

Glasgow life clearly suited him. What else did Bill get up to? "I went to listen to Crystal Clarke's boyfriend play jazz downstairs in a very nice pub, the name of which I can't remember. He was playing with five friends all of whom were sensational."

Bill also caught a gig by Rutherglen band the Fast Camels at the Hug and Pint on Great Western Road. "Mark – one of the crew who was detailed to look after me – is the lead guitar player with the band. They are, and this is my quote, a 'post-punk power pop outfit of the highest order.'"

Ordeal by Innocence begins on BBC One, Easter Sunday, 9pm