GRAY O’BRIEN is a man in motion. He’s leaping into the unknown and seeking out fresh adventures. When we meet in a Glasgow hotel on a drizzly Tuesday afternoon, the 48-year-old actor – known for his roles in Casualty, Peak Practice, River City and as dastardly Weatherfield businessman Tony Gordon in Coronation Street – admits his brain is whirling with possibilities.

First, though, we’re here to talk about his role in ITV drama The Loch which will see O’Brien return to our screens this Sunday. The six-part murder mystery, filmed at Loch Ness, Glencoe and Glasgow last summer, centres on a serial killer stalking a remote Highland town.

Breaking Bad star Laura Fraser plays police detective Annie Redford, with O’Brien as her brooding Nessie tour boat operator husband Alan alongside a cast that includes Siobhan Finneran, Don Gilet, John Sessions and William Ash.

O’Brien had to grow a bushy beard, learn how to skipper a boat and even do a spot of curling for the part. “The most amazing thing on the shoot was that Will Ash and I got to pilot these boats,” he says. “We had great fun. We were on Loch Ness for two days. It was just fabulous.

“The swell turns the boat so that every time you look up it is a different view. The light changes by the second, you look at something and it is brown, then green and then orange. It was incredible.”

Glencoe is somewhere he knows well, having spent many weekends walking and camping there with friends as a teenager. O’Brien was a keen Munro bagger – he has climbed 58 – until hip issues around 10 years ago curtailed his climbing ambitions.

“I had a hip replacement when I was 39 and that put paid to it,” he says. “I got both hips done about a year apart. I was shooting Doctor Who and every night after filming was going to see physios and chiropractors.

“I thought I had slipped a disc in my back but it was all referred pain. I went to [an orthopaedic specialist] who said I had collapse in both hips and needed surgery.”

O’Brien is philosophical. “It is just one of those things,” he says. “The only time I really feel it is when it is cold.”

The second youngest of seven children, O’Brien was born in Glasgow and lived in Drumchapel before moving to Stewarton, Ayrshire. His late mother Anne was a postwoman in the town, while his late father Eddie worked as a joiner.

O’Brien studied at the Royal Scottish Academy of Music and Drama, now the Royal Conservatoire of Scotland, just across the road from where we are sitting. “This August it will be 30 years since I started there,” he muses. “The industry has changed so much.

“Then, you came out of drama school in the hope you would go to Dundee or Pitlochry and do some rep theatre, or might get an episode of Taggart or Take the High Road. Actors very rarely left Scotland at that point.”

O’Brien landed a part in Taggart and went on to carve a successful television career. He played dashing Dr Tom Deneley in Peak Practice and had a recurring role in River City before being catapulted into the public psyche as Coronation Street baddie Tony Gordon.

“Coronation Street was a game-changer for me,” he says. “You know how big that character was. It was absolutely bonkers.”

Yet his success proved a double-edged sword. When the character was killed off in 2010, O’Brien found himself in resting actor limbo. “For the first six months I didn’t even think about work because I knew the phone wasn’t going to ring,” he recalls.

“Then the next six months it didn’t ring either and going into the second year it still wasn’t ringing. When it gets to five and six years you are thinking: ‘What is going on?’ People feel they can’t touch you because you are just too well known as that character.”

His biggest regret, says O’Brien, is never following up on an offer from the late author Jackie Collins to pass his showreel on to the makers of hit TV show The Sopranos after the pair met on Paul O’Grady’s Lily Live! comedy series in 2000.

“I was still this wee Weegie thinking that someone is going to tap me on the shoulder and say: ‘You’re in the wrang queue, son. You shouldnae have really been to that RSAMD …’ So I didn’t do anything about it,” he says.

Some weeks later O’Grady called him. O’Brien morphs seamlessly into the comedian’s famed Scouse accent as he recounts the tale. “He asked: ‘Did you send Jackie that tape?’ I replied: ‘Naw …’ and I won’t tell you what word he called me. That was a big lesson for me.”

In recent years, O’Brien has found steady work doing theatre including playing Captain von Trapp in Bill Kenwright’s production of The Sound of Music. It is something he clearly enjoys, even if he concedes to have missed out on TV jobs due to touring commitments.

He views the increasingly “saturated” industry as a numbers game, with many thousands of aspiring actors graduating from courses across the UK each year compared to the few hundred annually when he was starting out.

“It is very hard now in this business. The reason I think it is such a difficult game is that we are at least four times, possibly more, the ratio of actors to jobs. It is really overcrowded.”

O’Brien, though, considers himself to be among the fortunate ones. “I think there are only maybe two of the actors I trained with who are still in the business. I have been very, very lucky,” he says, grinning, while superstitiously touching all the wooden surfaces around him.

“I have made a living from this and I’ve never had to do anything else, but that could all change, you just don’t know, and I’m getting to that big number next year …”

A milestone birthday looming – 50 – isn’t the only reason for pausing to take stock. There have been other seismic shifts in his life of late. His mother Anne died last year and the grief is still palpable.

“It has taken me over a year to come to terms with it,” he says. “I was very close to my mother. For the last 10 years that’s what I did on a Saturday night, I sat in with my mum. I really miss her.”

Since splitting from his wife Lynn in 2006, the couple have always maintained an amicable relationship for the sake of their son Conor, now 17.

“My ex-wife has a new boyfriend and I’m so happy for her, but for some reason she has decided that we need to move on,” he says. “That was all a bit sad. It happened in the last couple of months.”

O’Brien insists there is no animosity – “I’m absolutely thrilled and hope my ex-wife understands how pleased I am for her that she has found some happiness” – adding that he has embraced it as a much-needed catalyst for overhauling his own life.

The actor has newly sold the house in Kilmarnock that he has called home for almost a decade and is ready to close what has been a tricky and often tumultuous chapter.

He will be based near London initially, but aims to try his hand at the US market. “I have sold the property and released some capital so my plan is to go and be able to live in America for a couple of years with no pressure.

“I don’t need to book a job immediately. If it happens, it happens. I don’t need to go out there and wait tables or work in a bar. This business is a lottery ticket. You don’t know when you are going to get the phone call.”

O’Brien recently found some peace too after turning to a medium who, he says, passed on a message from his late mother that he needed to move forward.

There’s a catch in his voice, tears pricking his eyes. “It was a really big moment for me because of the finality of it,” he says. “It was then that I wept, let go and realised that was it. I had held on to it for a whole year. I feel so much better and a weight has lifted.

“I didn’t believe in any of that stuff before. I thought it was all bulls***, but it has helped me. This is my time for living and moving on. I’m ready for the next chapter.”

The Loch begins on STV, Sunday, at 9pm