He has no regrets about leaving them wanting more of Chapman's swoon- inducing sternness. "Where would it have got me?" he asks. "If I was still doing it, what would I be adding to what I've already achieved? Chapman's done. It's like a session musician being asked to play the same set every night."
Those just about recovering from his departure from Casualty should brace themselves for another wrench. Le Vaillant is set to pronounce dead another drop-dead gorgeous tele medic - Doctor Paul Dangerfield from the series of the same surname.
"Most actors by definition have the desire to be something other than themselves," he reasons. "The principle is to diversify and go on assuming different identities. It's inherent in all of us."
With its predictable format - police pathologist steers four-wheel drive through picturesque countryside on the way to solving mysteries which baffle PC Plod - Dangerfield has become one of BBC1's ratings bankers. It is also the BBC's seventh most popular programme abroad, outstripping even Wallace and Gromit.
It provides the commissioning editor's dream tickets of cops and docs. "It's a rich vein to tap into," Le Vaillant explains. "The two professions work in areas that expose them to incidents the rest of us hardly ever have. How many of us have seen a dead body? There is a mystique about and a respect for people in that area. The stuff of drama is usually that which is other than our everyday experience."
The very popularity of Dangerfield means that quitting it is a risky business for Le Vaillant. That may be, but he is not going to miss the exhaustingly tight schedule of TV drama.
"Initially on the shoot of Dangerfield, we had a heavy-handed approach from the accountancy department," he recalls. "The proper place for them to be during a film is in the office with their accounts. They know bugger- all about filming.
"We've had a period in which the accountancy principle has been dominant," he continues, "and the arts have suffered from a dearth of imagination. No one wants to see Rocky 532 - that's an accountant's decision. You don't get a flowering of talent if the industry is market-led. As Janet Street-Porter said in her MacTaggart lecture the other year, the industry is talent-led or nothing. The explosion of pop in the 1960s didn't happen because the singers had all been to management school."
The actor has a similar disdain about the increasing vogue for market- testing drama series. "The idea of playing market research before creative imagination is despicable," he rails. "That is putting the cart before the horse. Van Gogh didn't ask people how to put his paintings together. Now they sell for $37 million. What price market research?"
Le Vaillant has nothing lined up yet to follow Dangerfield. Perfectly content to wait for the right project, he is no stranger to lean periods. He once survived financially by performing exerts from Shakespeare at Selfridge's. "The Seven Ages of Man speech used to be interrupted by people asking for directions to the sports department," he recalls.
Le Vaillant's only worry seems to be what they will call his series once Doctor Jonathan Paige (played by Nigel Havers) became its focal point. "How about Where's Dangerfield?" he asks with a grin.
The new series of Dangerfield starts on BBC1 next Friday.Reuse content