One to watch: The Great Sport Relief Bake Off - BBC Two, 8.30pm

That, in a nutshell, is The Great British Bake Off, which has surprised many by becoming one of the BBC’s most successful shows in recent years.

It all began with humble beginnings in 2010. Nobody expected it to be massively popular, but it proved to be a slow-burner, starting with around two million viewers, then gradually adding another million for the final won by Edd Kimber.

An average of 4.5 million watched the second series, which saw Joanne Wheatley crowned the nation’s best amateur baker. Over seven million watched John Whaite’s victory in series three, while 9.1 million tuned in to the series four finale won by Frances Quinn.

In fact, it’s now so popular that it will move to BBC One for this year’s fifth series.

“Television is a team game, and our Bake Off team, on screen and off screen, work incredibly hard all year round to make a show that we hope people will enjoy,” says the programme’s executive producer, Anna Beattie. “Figures like this are the icing on the cake. Our congratulations to the bakers, and thanks to everyone who has watched and enjoyed our series.”

But before that, newcomers (and long-standing fans) can get a brief taste of what to expect via this spin-off, which sees various famous faces baking away while trying to raise money for Sport Relief.

The first such fundraiser took place in 2012. Angela Griffin was one of the celebrities who took part.

“Oh my god, I loved doing the Bake Off!” she grins. “If I could apply for the proper one - I know I’d never win - but the experience would be fantastic. You just learn a lot from Paul and Mary, who are just such experts. I loved it, and I love watching it too - it’s just wholesome, isn’t it?”

It is indeed, and that’s perhaps where much of the show’s appeal lies - there’s no cynicism or nastiness involved, even if judge Paul Hollywood does get a bit grumpy about soggy bottoms (of the pastry variety) or dry sponge from time to time.

Veteran cook Mary Berry is the sweet to his sour, always offering comfort when things have gone not quite to plan, and encouragement and praise at other crucial moments.

This week, a batch of 16 celebrities enter the famous tent across four episodes of hotly contested competitions.

First up are former England cricket captain Michael Vaughan (who’s no stranger to talent contests, having appeared in Strictly Come Dancing in 2012), actress Samantha Bond, Harry Potter star Bonnie Wright and presenter Johnny Vaughan (no relation to Michael), who prepare sandwich biscuits, tarte Tatin and a novelty cake depicting a sporting landmark.

Those appearing in the rest of the week’s episodes are Kirsty Young, Jane Horrocks, Greg Rutherford, Jason Gardiner, Michael Ball, Emma Freud, Jamelia, Victoria Pendleton, Alistair McGowan, Rochelle Humes, Doon Mackichan and Helen Skelton.

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