"The place I was in was a real dump and I asked to be moved," he explains. What's this? Perrier winner turns prima donna?
"God, no; at least I hope not." Tiernan smiles anxiously, before going into a long ramble about how he needs to feel comfortable; how he normally stays at a lovely B&B in Kentish Town, and how he once asked for part of his fee to be spent on a better hotel.
No one could accuse Tiernan of self-importance. He may cut a commanding, Jack the Lad presence on stage, but off it he's shambling and hesitant. It's as if he's happier giving a performance version of his persona than grappling with the real thing.
There's something quite touching about this. It would be easy for him to provide good copy by doing what he does for a living - spinning a few yarns - and giving away little of himself, but part of him isn't satisfied with this. He wants to tell the truth, but he finds it painfully difficult, and he often appears to be talking to the floor or hiding behind his mop of curls rather than looking you in the eye.
But don't get taken in by his boyish vulnerability. Behind the soulful "mother me" eyes is a resourceful single-mindedness. You'd be hard pushed to get Tiernan to do anything he didn't want to.
"I like to control how close I get to people," he admits. "I shy away from those who aren't prepared to move at my pace. On stage I feel in charge; and when it's going well I feel loved."
Becoming a stand-up comedian is a singularly masochistic career move for most people in search of love, but Tiernan has led a charmed life. While others plod around the comedy circuit year after year going nowhere very much, he has gone from complete beginner to Perrier winner in three years flat. He's even found his way on to Father Ted.
You don't get this far without being funny, and Tiernan is very funny. What's more, whether he's talking about religious loyalties, terrifying schoolteachers or ruinous father figures, he's always engaging.
Tiernan didn't set out to be a stand-up. After leaving school in Galway, he came to London to work on a building-site. This was much too much like hard work and he skipped home after three months. Three years ago, aged 26, he reckoned comedy might be a bit of a crack.
"There was this pub in Galway that did lunch-time theatre, and I talked the owner into giving me a half-hour slot for two weeks. I can't say I was an immediate success; out of the 30 minutes, I reckon I had only seven minutes of decent material. So I built on this, and then did another show two months later. By this time I had about 15 minutes of good stuff, and I felt confident enough to take on the Dublin clubs."
The way Tiernan tells it, you get the feeling that his success was owed partly to luck, and partly to the accessibility of the Irish circuit.
Like many comedians, Tiernan isn't so keen to dwell on the part that ambition has played. It's un-arty, un-hip, un-alternative and deeply unattractive. But scratch the skin of any comedian - Steve Coogan comes instantly to mind - and you'll find naked ambition and competitiveness. And Tiernan is no exception.
When he describes the time he had with half of Ireland accusing him of blasphemy after an appearance on The Late Late Show, he comes on like an ingenu.
"I did this frivolous routine about the Lamb of God being a real lamb that the other lambs hated, and Jesus saying: 'I can't, I'm stuck,' when challenged to get down off the cross. Suddenly the studios were being picketed. It wasn't really worthy of scrutiny."
Which sounds fair enough until you consider that The Late Late Show is the forum for middle Ireland and this was exactly the sort of material that was guaranteed to generate a stir. As a way of getting media exposure - not to mention a wealth of new material - it could hardly have been bettered.
Tiernan talks of how originally his act was geared only to getting a laugh, but how he now tries to go beyond that.
"I want to feel as if I'm giving something of myself," he says.
This would sound hopelessly naff from most people but from Tiernan it seems genuine, because his material takes a long time to develop and comes at some personal cost.
"I've changed a great deal over the last three years," he says. "Performing can be an emptying process, and I've become much more morose and self- contained."
So what is he like at home? "I imagine I'm a difficult sod, but I don't know, as my partner hasn't said anything, and I'm too scared to ask."
Tiernan is no angst-ridden neurotic, and if a spell in solitary is what it takes, then it's a price he's clearly happy to pay. The only thing that does genuinely appear to worry him is that - to use his own words - "I will disappear up my own arse".
There doesn't appear to be much chance of that at the moment, but you never can tell. So catch him now.
Tommy Tiernan is at Her Majesty's Theatre this Sunday at 7.30pm. (0171- 494 5558)Reuse content