Monty Python fans love the musical show Spamalot which, as the posters proclaim, "lovingly rips off Monty Python and the Holy Grail".

This is the legendary tale of King Arthur and the knights of the Round Table... but includes beautiful show girls, cows, killer rabbits and French people. Sadly, witch burnings have been cancelled because they're too expensive.

Surprisingly, given its success on Broadway, in the West End and now on tour, Bonnie Langford hadn't seen the show until a few weeks ago.

After a week's rehearsal she found herself standing on stage as The Lady of the Lake.

"I was slightly stunned. The show moves at the speed of light," says Bonnie. "Eight pages of script goes by in about eight minutes. And I'm still trying to work out who's coming on and who's playing what because many of them play more than one part.

"It was very daunting on the first night when I was not sure what comes next. Everyone is running around like clockwork. I felt a bit like a rabbit in the headlights. But it's a great, fun company. And Todd Carty is adorable."

Spamalot is written by Python Eric Idle and composer John du Prez.

It is, however, constructed like a "proper" musical (albeit a comic one) with songs including He Is Not Dead Yet, Knights Of The Round Table, Find Your Grail and the song a Reader's Digest poll named the nation's favourite comedy song – Always Look on the Bright Side Of Life.

"This show covers such a broad spectrum of style," says Bonnie. "It's like a Gilbert and Sullivan operetta, then it's gospel. Very few shows can do that, but here you are invited into this parallel universe.

"I was certainly aware of Monty Python when I was growing up – the cartoonish element and the big foot. It was the realisation that grown-ups could be silly too. And everyone knows the Dead Parrot sketch.

"You can't be British and not be aware of it, but it was not something I went out of my way to follow.

"This show takes the best bits and then moves on. The trick about this show is that it's so speedy. They don't linger. They do sketches then it's on to another one.

"It has every old gag in the book. It's just silly. It's quite nice to be a grown-up and just be silly. I thought, I have to do this job.

"It's one of those shows you have to do with an audience that understands. The audience go crazy at the end. They stand up, all howling with laughter."

Spamalot marks quite a departure for Bonnie. She started as a child star (Bugsy Malone, Just William) became Doctor Who's assistant and thrived in musical theatre – Cats, Chicago, Sweet Charity, Gypsy – and in 2006 starred in Dancing on Ice.

Spamalot is certainly hard work, but Bonnie loves the "craziness".

"It's sort of like a pantomime – a tribute to British eccentricity. It's great to be doing the tour. I've been in America for a couple of years. The last tour I did was Guys and Dolls.

"I have to be really organised, but I'm looking forward to Torquay because it's half-term and my husband and daughter will be with me."