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

Nighy, 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 at Ardgowan Estate near Inverkip – and, in true 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 Nighy. "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 Nighy. "It was great and one of the nicest jobs I have ever had," he says. "Not least because Sandra Goldbacher, the director, is exemplary – sensational, lovely and smart as anything. She kept a friendly, cool atmosphere on set.

"Also, the cast were adorable. Crystal Clarke was enchanting, Ella [Purnell] was marvellous – they were good fun. Morven Christie was sensational. They were all in good form.

"I said to Anna [Chancellor] as we sat at either end of the family dinner table: 'Look at us, we're made for each other' and it is surprising that professionally I had never been married to her before. She is wonderful."

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Nighy 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, Nighy 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 Nighy 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 of Glasgow during filming, Nighy 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 open the drawer 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 Nighy. "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."

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Nighy is twinkly-eyed and good humoured with oodles of charisma. The word droll should have a photograph of him next to it in the dictionary.

When I arrive, he apologises for his "spooky handshake". Nighy suffers from Dupuytren's contracture, a condition caused by the shortening and thickening of bands of fibrous tissue in the hand making some of his fingers to bend inwards towards the palm.

It is a hereditary disorder. Does he recall any relatives having it? "I think my grandfather," says Nighy. "It is in my family."

Surgery can correct it. He holds up a hand. "I had this one done twice – that was a long time ago – but it came back. They cut my mother's little fingers off: she was used as a kind of guinea pig."

Nighy insists it isn't painful. "I get by – apart from giving me a spooky handshake."

The youngest of three children, Nighy grew up in Caterham, Surrey. His late mother Catherine was a psychiatric nurse.

"There were two or three psychiatric hospitals near us and they were the big source of employment. It is probably why there was a considerable Scots and Irish community there because they came for the work. It was a strange job, but in terms of holiday money and a pension it was a good job."

As the daughter of two nurses myself, I reckon it can instil a certain staunchness in life. "I think you might be right," he agrees. "My mother was not overly impressed by bruises or scratches. She would say: 'C'mon, wash yourself and get on with it.'"

His late father Alfred was the works manager at a garage and the family lived in an adjoining house. "You would open our front door and there were the petrol pumps," says Nighy. "He was a very rare and wonderful man, my father.

"He died when I was 26. It was unnecessarily early. He died of a heart attack, something he wouldn't have died of now; they would have been able to save him. He was 64.

"Like a lot of people – and I would like this remark to be prefaced by that because I know that there are many, many people who would say the same thing – one of my great regrets is that my dad didn't get to enjoy any of the things that have happened to me.

"To say he would have got a bang out of it, does not cover it. I miss him. He is the major influence on my life. I had done a job where I had to get my hair cut and when I came home, my mother went quiet and sat in the bedroom for a while.

"When she came out, my mother said: 'I'm sorry, but you look so much like your father.'" Nighy holds my gaze across the small table. "You are basically looking at my father."

There are other echoes of his father. "My personal style, such as it is, is almost entirely based on my dad." The sharp suits? "My father was always very well turned out. My elder brother was a great influence on me as well in terms of suits.

"My brother and I shared a bedroom when I was very young and when he was out I used to have a look in the wardrobe. For work, he would have several suits. He was also in a band and a great singer.

"He was very good-looking, he still is – make sure you put that bit in – and successful round our way. He had sharp suits and when he was out I would have a look and slip them on from time to time." There's a smile as he says it. "But don't tell my brother that."

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Nighy has worked with many Scots over the years: James McAvoy, Kelly Macdonald, Morven Christie and Gregor Fisher to name but a few, "And I've had very, very good experiences with all of them," he attests. "I think it is because of my mum."

He catches himself. "Obviously, it is because of my mum, but I do pay attention when I hear a Scottish accent, particularly a woman with a Scottish accent. There is something goes off in my head."

A recent study reported that the amount of dialogue women get in Hollywood films decreases after the age of 40. What are Nighy's experiences as a man growing older in the industry?

"Quite often with casting I think: 'Well, where would you put me?' Then there is another part that seems to suit and I'm always slightly surprised. You do think: 'Well, I'm quite old. You can't give me a gun – well, only in a comedy way.'"

A playful expression crosses his face. "I quite like the idea of being a terrible, clumsy MI5 agent or something like that," he muses.

"I'm bound to say this, but it is true: I'm extremely fortunate that they keep finding parts for me. This is not me being cute or coy or modest, it is just the fact: I am not over being grateful for what has happened to me, so I have no beef with anything.

"I remember sitting in a cafe some years ago and thinking: 'From now on, you cannot complain …' Not that I was in the great business of complaining.

"Sometimes you will read the script and the part for the young man is such a blinder, you think: 'God, I wish I was 41.' But only very occasionally. I'm fortunate."

What about being asked to do sex scenes, has that changed as Nighy has got older? "You keep thinking that it must be over," he nods.

A lot of actors have a no nudity rule. "I think that is a very sensible way to be," he says. "Often it is to do with the budget, what I mean is commercial things, and it is usually to do with exposing women.

"There is no need for most of them [sex scenes and nudity]. There is no plot to which it is essential that we see a women's breasts or any other part of her body. Unless you are doing something in a nudist colony, but not the ones that we're discussing.

"I sound like my father because he used to say: 'There were very erotic things and you never saw anything, they were sexy and exciting …' It is true. Obviously. That is what constitutes eroticism. It is the bit before that is always the desirable part."

It is fascinating to hear him talk frankly on the matter. "I have been asked to be naked a few times," continues Nighy. "I don't know why. Just lately. Not me particularly, but there have been scripts.

"There are a lot of films now and I know it is because of the success of The Best Exotic Marigold Hotel. Which is great because it means they have discovered that you can make films about people over a certain age and there is an audience.

"Obviously, because of my age, I get a lot of those scripts and some of them are good and some aren't. Some of them which aren't so distinguished are sort of like 'you're not dead yet' movies and apparently the quickest way of showing you're not dead yet is to get your clothes off.

"You think: 'Well, OK, you can get someone else to do that …'"

Nighy's own career has been described as a game of two halves – or rather Act One and Act Two to use acting parlance. His early work comprised meaty theatre roles and smaller TV parts including Kiss Me Kate and Auf Wiedersehen, Pet.

Then in 2004, at the age of 54, things changed almost overnight when he won two Baftas, one for playing a newspaper editor in the BBC drama State of Play and another for the role as a washed-up yet lovable rock star in the Richard Curtis-directed film Love Actually.

"I do know my money went up," he says. "Because you become more visible and are therefore more valuable and castable and useful. You can play a principal role in a movie.

"It is one of those Catch-22s where you can't play a principal role in a movie until you have played a principal role in a movie. And how are you supposed to do that?

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"I have always been incredibly fortunate," he adds. "Again, that is not me being cute. That is just facts. I have nearly always had a job. And not only have I nearly always had a job, but also had a job I would be quite proud to tell my grandchildren.

"I've also done some things which I am very glad were done on early tape which is now corroding somewhere in a basement because I have done some dreadful things – or rather I was dreadful in some things when I was young – and fortunately those things might not have survived."

Becoming highly bankable was not the only major shift. "The big thing after Love Actually and State of Play was that I didn't have to audition anymore," says Nighy. "Auditioning is absolute murder. That is a big deal, ask any actor.

"It completely turns around and it is then people trying to persuade you to do jobs – instead of you trying to persuade people to give you jobs. That is the biggest thing that can happen to any actor."

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