'You can't fool children," says the nation's favourite kids' entertainer and its finest exponent of the three Cs of children's broadcasting: "My very first commissioning editor at the BBC, Ian Lockland, taught me that it's all about clarity, contact and commitment. It's not always easy for a single person to look through a lens in a studio and engage with a child at home but I just really enjoy what I do and I hope that comes across in my performance. I genuinely love it."
In the space of an hour, Justin Fletcher, 41, whose colourful roll call of characters includes Anna Conda, Arthur Sleep, Gail Force and, of course, the inimitable Mr Tumble, uses the phrase, "I love it," more than the average four-year-old whines, "I want ..." before breakfast.
He radiates enthusiasm for his genre and not in the often manufactured manner of scores of younger presenters who have at least one eye on their next "adult" presenting gig.
"I've been doing this for 16 years," he says. "This is not a stepping stone to other things and daytime telly. I've always loved performing and I knew in my first year at drama college that I wanted to do children's television."
As one of five children of the celebrated songwriter Guy Fletcher, who wrote hits for Elvis Presley, Tom Jones, Ray Charles and Cliff Richard, and now chairs the Performing Rights Society, Justin was born into performing at the family home in Berkshire.
"I was brought up in that kind of creative world and I got to meet some very interesting people," he says. "Dad wrote Cliff Richard's 1973 Eurovision Song Contest entry, Power To All Our Friends, and Cliff came over a few times. I was only three then but my big sister Juliet was madly in love with him and used to hug him and not let him go.
"Rick Wakeman was a regular visitor and Ron Goodwin who scored the movie Where Eagles Dare and Les Reed, who wrote Tom Jones's It's Not Unusual, would use the studio in the house. I was fascinated by all that."
Despite piano lessons as a boy, Justin's creativity veered away from music. "From as early as I can remember I was much more into creating characters," says Justin, who plays 26 different ones in his sketch series, Gigglebiz. "I used to write little characters down and observe people. Particularly schoolteachers. I was quite good at mimicking people. But what really started it off was my dad giving me his Super 8 cine camera. That was it for me. I was out there making my own films. I'd save all my pocket money to buy Kodak Super 8 film, which you then had to send off to the lab – it took a week to get it back … the excitement ... it was too much."
Justin's childhood TV heroes will be familiar names to anyone brought up on 70s TV. "I was a huge Muppets fan but the real gods were Derek Griffiths and the guvnor, Brian Cant."
Mere mention of Cant, whose effortless affability and gentle humour endeared him to millions, provokes an almost reverential response. "Brian Cant has got a huge amount to do with what I do now. He's the man. A brilliant performer. I used to watch these guys and observe them very carefully because they were so good. So engaging."
A keen student of visual comedy, Justin's inspirations date back long before the 1970s. "I used to wear out VHS tapes of Laurel and Hardy and study those little looks to camera. I incorporate that as a little homage to those guys. And obviously, Charlie Chaplin and Buster Keaton, too.Those silent stars were fantastic for using facial expression."
CBeebies celebrates its 10th anniversary as a stand-alone digital channel this year and Justin has been at its heart from day one.
Early success in slapstick showcases Tikabilla and Higgledy House, plus voice roles in Tweenies, Finley the Fire Engine, Shaun the Sheep and Thomas the Tank Engine (Justin's ring tone is a "choo choo" train noise) led to comedy vehicles Gigglebiz, Jollywobbles and, most recently, the Crackerjack-style Justin's House.
But the show that has earned him two Baftas and an MBE is the pioneering Something Special, featuring Mr Tumble and using the Makaton signing system, to help relieve the frustration of children with speech difficulties.
"It's such an important show," says Justin. "We get letters daily saying, 'My child has spoken for the first time after watching that programme.'
"And children of seven or eight who struggle talking can engage with that programme – it really helps them. I'll be doing the CBeebies live tour during the Easter holidays, but after that we're filming the eighth series of Something Special and we have to keep it going."
That is great news for Mr Tumble fans. More surprising news, perhaps, is the revelation that the playful red-nosed joker who brings Justin so much attention – "One of the Queen's guards even shouted out 'Mr Tumble' before I met her," – was partially inspired by the smutty 1980s DJ and sketch-show king, Kenny Everett.
"Mr Tumble was an amalgamation of an idea the commissioning editor had for a character who signed and an old character I'd been touring schools with, called Professor Muddles. We shot the first pilot show against a plain white studio background and that simplicity reminded me of the Kenny Everett sketches. Nothing was cluttering the screen and kids can engage easily with that.
"I loved Kenny Everett. I thought his sketches were fantastic. My dad used to write music for them and even appeared in the background as a pianist in a few. Those sketches worked because they were clear and simple, and it's the same with Mr Tumble."
Such is the popularity of Mr Tumble that Justin is planning a feature-length movie version, hopefully including cameo performances from some of his celebrity admirers, among them Gary Barlow, Simon Pegg, Peter Kay and Johnny Depp.
"I've stayed in touch with Gary Barlow, since we met at the Baftas, and I've had supportive emails from Simon Pegg and Peter Kay, both of whom I love, and I've been told that Johnny Depp brought his kids to a show I did in Bath, so it would be great to get them all involved. I've got a nice idea about Mr Tumble going through a regular day and coming across hundreds of children, like a kind of Pied Piper character, and I think it could work internationally, too, as there's minimal dialogue so there's no language barrier. Mr Bean is huge in places like Asia – and look at the success of The Artist."
Should a silver-screen Mr Tumble bring Justin global recognition, one thing you are unlikely to see is the star of the show falling out of a nightclub at 3am. "I've gone through that whole stage of going out quite a bit and I just like to spend time quietly with my friends and family who all live in and around Berkshire," says Justin, who is single, and has no children of his own, but is a popular uncle to his four siblings' children. "It can sometimes be difficult to switch off with so many different characters swimming round in my head but when I get home I just like going out to sort out the fish in the pond in my garden. I'm just a regular guy.
"Getting up early and being sparky in front of a camera at 8.30 in the morning isn't a problem for me. I'm conditioned to do it and really love it.
"I'm doing what I really want to do. I'm really blessed by the amount I've already done and you can't beat watching a child's face light up when you're doing a character or a song. While I've still got the energy and the ideas I'm going to keep going – I just love it."
CBeebies Live! tours the UK from 31 March to 14 April. Justin's new album Hands Up is released on Monday
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