At five foot three, Barrie was rather shorter than the nearly six-foot Glasgow-born actor familiar from his TV turn in American hit Ugly Betty. As Riddell prepares to play Barrie in Peter and Alice, a new play by John Logan directed by Michael Grandage, the power of imagination will clearly come into play. But when other portrayals of Barrie have included Johnny Depp in Finding Neverland, Riddell shouldn't have too much of a problem.
"He was described by most people as this strange little creature," Riddell explains, "and he had this really strange voice, but we don't want to be too weird about it. He was a very complex character. One minute he could be witty and charming and captivating to the boys, the next he could go into these black silences, and there's a real darkness about him. It's a very short time in the play to try and capture all that complexity. There are obvious comparisons there as well with Lewis Carroll and both men's obsession with childhood, but I don't think Carroll had as much of a troubled childhood himself as Barrie did."
Peter and Alice is based on a meeting between Peter Llewelyn Davies and Alice Liddell Hargreaves, who were the inspirations for Barrie's Peter Pan and Lewis Carroll's Alice, arguably the most captivating of children's characters ever written. Logan spotted a line in a biography of Barrie that suggested the pair met. In the course of the play, set at the opening of a Lewis Carroll exhibition in 1932, both authors make an appearance.
The Tony award-winning writer's play forms part of a season by the Michael Grandage Company, and sees Riddell acting alongside Judi Dench and Ben Whishaw in the play's title roles, with younger actors playing their fictional alter egos.
"It was a no-brainer doing this," Riddell says. "Just because of the people involved apart from anything. Michael Grandage is an inspiration. He puts you totally at ease."
Riddell first came to prominence in Annie Griffin's comic drama series The Book Group. This led to being cast as hospital lothario Jamie Patterson in No Angels, which focused on the messy love lives of four nurses who broke the Florence Nightingale stereotype with abandon.
Riddell still stays in touch with his former No Angels colleagues, and last week was at a birthday party attended by Kaye Wragg, Louise Delamere, Sunetra Sarker and Jo Joyner. In keeping with the programme, it was a typically wild affair, with current EastEnders star Joyner using her wiles to access the Queen Vic Suite in the St Pancras Hotel for after-hours revelry.
Riddell, alas, was unable to indulge as much as he'd like. "I had filming in Bristol in the morning," he says, "so I just left them to it."
A year after No Angels, Riddell was cast in the American therapist-based drama, State of Mind, which led to a semi-regular role in Ugly Betty, playing the love interest of another Scottish emigre Ashley Jensen.
"That was probably the first time we'd worked together since we did The Big Picnic," Riddell says of Bill Bryden's First World War spectacular, which was performed in the Harland and Wolff shipyard in Govan in 1994."
That was at the start of a stage career that has seen Riddell appear in Aileen Ritchie's The Juju Girl at the Traverse, and The Cosmonaut's Last Message to the Woman He Once Loved in the Former Soviet Union, by David Greig, at the Tron. Riddell also appeared in another David Greig play, Victoria, with the Royal Shakespeare Company, and David Harrower's Knives In Hens at the Royal Exchange, Manchester. With such a pedigree, it's perhaps surprising that Peter and Alice will be Riddell's first appearance onstage in seven years.
"It was time to do theatre again," he says, "or else I'd never do it again, because it would become too scary. So it's a real novelty for me again after so long out of it."
When we speak Riddell has just been inspired by going to see Glasgow Girls, Cora Bissett's asylum seeker musical, during its London run. "It made me feel very old watching it," he says, "but the energy of it was incredible."
Riddell is happily domiciled in London again following two years in America, and with such high-profile Scottish drama as Glasgow Girls making waves, one wonders how long it's likely to be before audiences see Riddell back on a Scottish stage again.
"It's difficult," he admits, "because I've got family now, which is part of the reason why I've not done theatre for so long. The thought of being away from them isn't appealing. But because I trained down here in London, I've never really been part of that Scottish theatre scene, but I'd certainly be interested in working there if a part or a play that I loved came up."
Casting directors should take note of the sort of thing which might tempt Riddell back across the Border.
"I love doing plays by American writers," he says. "There's something about them which really gels with the Scottish psyche, something about the passion. Years ago I played Tom in The Glass Menagerie, which I absolutely loved. As far as Shakespeare goes, I'd really like to play Richard III. Again, it's the intensity of it that appeals."
In the meantime, Riddell's portrayal of JM Barrie might act as some kind of calling card, even if he does seem a little star-struck by the company he's keeping.
"If we get it right, it could be quite magical," he says. "It's worth the ticket price for Judi and Ben alone. I'm completely in awe of them."
Peter and Alice, Noel Coward Theatre, London, Saturday to June 1. www.michaelgrandagecompany.com