WHEN Greg McHugh was a young drama student, he appeared in a couple of episodes of hit sitcom Rab C Nesbitt.

“I was so nervous to act opposite Gregor Fisher I couldn’t say my lines,” says the Gary: Tank Commander and Guilt star, with a groan.

“This time around, I still can’t say my lines – but I’m not as nervous….”

Greg and Gregor are starring together in Only Child, Bryce Hart’s six-part comedy series about a father and son thrown back together by circumstance.

Greg as Gary: Tank CommanderGreg as Gary: Tank Commander (Image: Graeme Hunter)

Greg plays bit-part actor Richard, whose long-overdue visit to his recently widowed father Ken makes him realise his dad may need some more help – even though Ken does not agree.

Richard’s relationship with his dad is "part frustration and equal parts guilt and love", explains Greg.

“It is complex,” he adds. “Richard loves Ken, Ken loves Richard but like all families, they don't get on all the time.

“And in fact, the more time they spend together, the less they tend to get on. Richard is an actor whose career isn't going terribly well.”

He breaks off with a laugh: “There's no reflection on me personally about this…”

There is a “real clash of characters” in Only Child, adds Greg.

Gregor FisherGregor Fisher (Image: Newsquest)

“There’s Emily, the neighbour who Richard quite fancies but doesn't know how to behave around; Digsy, the local, slightly mad man who can't stop stealing things – so a huge range of people that Richard has to navigate, via his dad, who's also driving him mad,” he says.

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“It’s relatable in that it's about a son who moves home to really look at the inevitable issue of parents growing older and how you have to cope with that and their idiosyncrasies.”

For Greg, working on the show has been “amazing.”

“I have absolutely loved it,” he says. “I hope the audiences enjoy it. Bryce Hart has written really beautiful scripts which have got heart and comedy.

“I think this is probably the closest I have played to myself in terms of a character. I'm not Richard, though, I do sometimes find him a bit annoying.”

He pauses. “Although, people might say that about me… I also understand the reality of coping with slightly older parents, who I'm very lucky to still have, but who are also maddening.”

Gregor, meanwhile, says he is “an absolute shoo-in” for the part of Ken.

“The relationship between Ken and Richard is quite a wee bit tricky because I'm maybe slightly dotted, old…” he says.

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“I'm maybe slightly on the eccentric side, shall we say. And he’s [Ken] a bit of a hoarder, and his memory isn't as sharp as it should be. A bit like me, actually. I’m a shoo-in for this part, these things are true of me.”

Working with Greg has been “pretty average”, deadpans Gregor.

“He's quite young, he's got a great deal to learn,” he jokes.

“He goes out at night. He turns up. He knows the words, he's not very good at hitting the mark. He causes a bit of trouble with the cameraman. And sometimes he stands in my light.

“I don't think it's deliberate.”

Only Child, which also stars Amy Lennox, Stuart Bowman and Forbes Masson, starts on BBC Scotland on November 21, and on BBC ONE on November 22.