Who needs a Tardis to time-travel when you’ve got a good agent? Former Doctor Who Peter Davison is sitting backstage at the Palace Theatre, still looking shellshocked at the thought of taking over from Simon Russell Beale as King Arthur in Monty Python’s Spamalot. But shellshocked, along with what he calls “dithery and incompetent”, is Davison’s default performance setting these days, and he does it brilliantly.

King Arthur is a departure for the 56-year-old, although he has sung onstage, playing Amos Hart in Chicago in 1998. “But I never counted myself as a musical performer,” he explains over curly-edged sandwiches. “When I used to audition I could never afford to pay a pianist so I’d accompany myself on the guitar. I didn’t get any of the parts. I was hopelessly lost.”

Davison was pretty lost when he auditioned, but it worked in his favour. “I went up for Spamalot and heard no more. Then the producers rang my agent and said, ‘Would Peter mind if we flew him to New York to meet the director Mike Nichols?’ I said, ‘Not at all.’ But I totally screwed up the audition. I started in the wrong key and got the words wrong, but I screwed it up in an endearing way and went ‘Oh bugger’, which was the Monty Python Spanish Inquisition pay-off. Mike said, ‘You cut out my favourite joke in the show’ but gave me the part.”

It is a piece close to his heart. “I was a huge fan of Python. I was 18 and it was like a breath of fresh air. . . I have a very definite idea of the way I want to do this character. My interpretation owes more to Graham Chapman’s film version than it does to Simon.”

The affable Londoner is best known for television roles.

The innocent vet Tristan in All Creatures Great and Smallbegat Doctor Who, which begat another doc in A Very Peculiar Practice before the gentleman sleuth Campion. And lest we forget, he wrote the theme for the children’s series Button Moon.

Things went slightly quiet in the 1990s when he split with his wife, Sandra Dickinson, but Davison (now remarried and with two small children and an adult daughter, Georgia) worked constantly, resurfacing in At Home with the Braithwaites and the sitcom Fear, Stress and Anger, for which he picked up a best actor award at the recent Monte Carlo TV Festival. On collecting it he announced that it was the first thing he had won “since being voted Top Man on the Multi-Coloured Swap Shop in 1981”.

There are few more consistent, harder-grafting television actors. “I admire actors who kept working,” smiles Davison as he spills coffee down his T-shirt. “James Stewart. Spencer Tracey. But there was no plan. Sometimes I wish there was. I just didn’t want to end up being one of those actors who turn up on UK Gold and you say, ‘Blimey, whatever happened to him?’ ” Maybe one of the reasons he was “tremendously excited” by Spamalot was that he was also tremendously available. Both Fear, Stress and Anger and his crimefighting vehicle The Last Detective have been axed. The sitcom’s demise, which Davison puts down to regime change, is particularly galling: “New people don’t want to pursue an old show because if it’s a hit someone else gets the credit. It’s a tragedy because comedy history is littered with shows that didn’t do well at the start. In today’s atmosphere The Good Life would have been cancelled after one series.”

Davison was a popular Doctor Who, but after three years, in 1984, he handed in his sonic screwdriver. “Every few months I’d see contemporaries doing different shows. They were probably envious of me, but I was envious of them and didn’t want to be typecast.” He initially steered clear of Dalek-related activity, but relented, reprising the Doctor for audio releases and attending conventions: “But I won’t dress up. I’m surrounded by people dressed as me anyway.”

Funnily, though, as we prepare to take photos, he dons a natty Panama hat. “I found this when I was clearing out my father’s things. It’s the sort of hat my Doctor Who wore.” Once a Time Lord, always a Time Lord, even when you are a king.

— Monty Python’s Spamalot plays at the Palace Theatre, W1 (0870 8900142)

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