And not just because he's hugely apologetic and likeable. He has one of the best excuses imaginable.
"I've been accidentally locked in the house," he says of his parents' home in Darnley.
"When I came downstairs I realised the door was locked and my keys were gone. My dad had taken them, not realising I was there.
"The taxi driver arrived at the proper time and I had to wave to him from the bedroom window just to go away. You can imagine how he waved back."
It's not hard to understand why his dad forgot his 24-year-old son was home. James left for drama college in London seven years ago and visits back to Glasgow have been rare, thanks to being so much in demand by theatre and TV producers.
Last year, he starred alongside Alison Steadman and Ashley Jensen in ITV drama Love and Marriage. This followed great acclaim at the Globe for Macbeth and on the West End in 2012 for Chariots of Fire.
More recently James appeared in upcoming BBC drama The Assassination of Franz Ferdinand and featured opposite Bill Nighy in The Worricker Trilogy of spy adventure.
Now, the one-time attendee of Pace Theatre school, in Paisley, is set to star in New Worlds, Channel Four's sequel to The Devil's Whore, alongside Jamie Dornan and Freya Mavor.
Set in the 1680s during the English Civil War, James plays Will Blood, the son of the man who stole the crown jewels, and the pair are sentenced to death.
Will tries to take the blame for his father, and is offered the chance to save his dad's life - if he'll spy on family and friends.
"The storyline is great," says James. "It gives me the chance to play a character facing a real dilemma."
He admits that landing major roles alongside film greats such as Nighy and Ralph Fiennes was incredibly demanding.
"When I first filmed Page Eight (the first of the Worricker series) I was just out of drama school and a bit nervous.
"I had a scene to enter a room and give the pair information but I couldn't work out whether to knock or burst right in and my palms were sweating, so I barged in and they called out 'Knock the bloody door'.
"And they were right. But they were great with me. And I learned the likes of Ralph Fiennes is so good because he's so focused on what he does.
"Learning this gave me the confidence to work on New Worlds, to learn to stay in the moment."
It's not just television that has become seduced by the young Scot. His next theatre role sees him play King James I in the National Theatre of Scotland's co-production with the National Theatre of three new plays about the 15th Century Scottish Kings.
The plays, about the lives and troubled times of James I, II and III by playwright Rona Munro, debut at this year's Edinburgh International Festival, before moving to the Olivier Theatre.
"They are the best plays I've ever read," says James. "They are unlike anything the NTS have done before. I've never been so excited about a job.
"And I get to play a man the director describes as a 'charming psychopath'."
What's clear is that James is hotter than Hades at the moment. But he's careful about the work he chooses.
"I want to do the right things to progress," he says. "I want to act in theatre or television that makes a mark. I'm not thinking about money or fame, that's not what it's about. It's about showing you can really act, becoming different characters"
HE adds, smiling: "I want to be Meryl Streep. She can alter herself so incredibly and I want the chance to do that."
James, who lives in Shoreditch, in London, would love to step into the darkness.
"At the Royal Court I played a 21-year-old who falls for a 12-year-old who had elements of psychopathy about him," he says. "I haven't played a Begbie (the deranged character from Train- spotting) yet, but I'm hoping."
But in spite of achieving remarkable career success so quickly, the gods of acting haven't been completely kind to the young man from the south side of Glasgow.
"When I heard I was to be in Worricker with Winona Ryder I'd planned to ask her to marry me," he says, grinning. "But I didn't get to do a scene with her and it didn't quite work out."
l New Worlds, Channel 4, Tonight, 9pm