SEVENTEEN million people every week are transfixed over breakfast by Mr Motivator, GMTV's resident exercise instructor - 6ft tall, a honed and toned mass of rippling lats, pecs, quads and triceps, all snugly packed into a psychedelic skintight Lycra leotard-thing. 'It's a one piece suit,' explains Mr M. He has around 150 of them, and they are a vital piece of motivating equipment.

'Guys should all wear stretch pants, they support you a lot better and you've got freedom of movement. When you're wearing shorts, believe me, it's very uncomfortable. Things hang down that shouldn't - really baaad. With stretch pants, you don't have to worry about people going 'Aaaaah] look at that]' ' At what? 'The beer gut . . . ha, ha]'

This upbeat Motivator chirpiness not only landed Mr M the GMTV spot but has shot his exercise video, the BLT (Bums, Legs & Tums) Workout, to the top of the video best-seller list. BLT went platinum last week - 130,000 copies have been sold, well over pounds 1.5m worth at pounds 12.99 per copy. This puts Mr M ahead of Clint Eastwood and Tom Cruise, who both have films further down the video charts, as his PR lady points out proudly.

The launch of BLT was well timed. At this time of year, exercise videos are especially big business, accounting for nearly 10 per cent of all video sales, according to Doug Hopper, market researcher at the British Videogram Association. 'It's New Year's Resolution time,' he explains. Even Zsa Zsa Gabor at 73 and Richard Wilson (aka Victor Meldrew) have hobbled on to the bandwagon (Zsa Zsa has enlisted two hunky body builders to get down to the sweaty bits in It's Simple, Darling - sadly only available in the US).

Mr Motivator still has some way to go before catching up with the exercise video front runners. Last year around 1.5 million exercise videos were sold. Most popular was Cher Fitness, which has sold over 350,000 copies since it was launched (over pounds 4m-worth at pounds 12.99 - price includes free elastic workout bands). This puts it into the top 30 best-selling videos of all time, along with Callanetics (800,000), Rosemary Conley's Whole Body Programme (400,000) and Jane Fonda's New Workout (350,000).

Perhaps the safe and simple Bums, Legs & Tums might signal the end of the usual perfect- woman-showing-off exercise tape. Alan Bryce, editor of Video World magazine, is pleased to see the BLT Workout. 'Mr Motivator makes a welcome change from the typical bimbo.' W H Smith spokesman Julian Graham-Wrack also feels there is a 'shift away from that perfect body look' - he points out that the current number two seller, The Y-Plan, actually features 'real people'.

Genuineness is certainly part of the Motivator repertoire. 'My smile is natural]

I love what I'm doing,' says Mr M, smiling very widely. 'There's nothing pretentious about me. This is not a persona that comes out of the cupboard - it's how I am. And if you radiate happiness, people zone in on it.'

His routines are punctuated with cheerful cries of 'Yeah] looking good' and 'Put smiles on your faces]' 'It's not my performance,' he explains. 'I'm keeping you motivated. Even five minutes of activity is good, so well done.' How can he keep this kind of cheerfulness going at seven in the morning? 'Am I on something? I'm on being alive] I like mornings. I like what I'm doing so I jump out of bed . . . don't you?'

Mr Motivator's first forays into fitness were in a church hall 13 years ago, in the distant days of popmobility, when his name was still Derrick Evans. He trained in the US, and belongs to the Fitness Professional instructors group. But, despite being so fit and tough, he won't be photographed outside in the cold (his one-piece is extremely brief round the back) and his first television slot (6.50am) is pre-recorded so he doesn't have to turn up quite so early at the studios.

Modestly claiming to be 'amazed' by the BLT success, Mr Motivator gets hundreds of letters a week from fans and is recognised wherever he goes. 'I get a wonderful feeling - everyone talks to me,' he admits, 'but I've got my three kids, they keep my feet firmly on the ground.'

His ambition is to take over a whole programme. 'I'd love to do a chat show.' Having a second string to your bow is a good idea in the faddy fitness business. 'It's very much a fashion thing,' warns Doug Hopper.

'Last year it was 'step', this year it's sliding and boxing - people get bored very easily.'

(Photographs omitted)