Gervais reveals his latest Extras

Comedian Ricky Gervais.

His comic creation Andy Millman is a wannabe actor frustrated by his inability to land anything other than bit parts in movies.

But in real life, Ricky Gervais has the clout to attract stars of the calibre of David Bowie and Orlando Bloom to appear in his sitcom Extras.

Coldplay front man Chris Martin, The Da Vinci Code star Sir Ian McKellen and television and radio presenter Jonathan Ross will also make cameo appearances in the second series of the BBC2 comedy due to air this autumn.

Thanks to the popularity of the first series, which featured guest appearances from Samuel L Jackson, Kate Winslet, Ben Stiller and Les Dennis, well-known names have been queuing up to play themselves in the sitcom.

The X-Men star Patrick Stewart, TV hardman Ross Kemp and footballer turned actor Vinnie Jones also appeared in series one.

In series two, Stephen Fry, Harry Potter actor Daniel Radcliffe, newsreader Moira Stewart, Ronnie Corbett, Germaine Greer, Richard Briers and Diana Rigg are also set to appear in the six-part series.

Negotiations are also underway to persuade Channel 4 chat show hosts Richard Madeley and Judy Finnigan to sign up and at least one actor from BBC1 soap Holby City will also make a guest appearance.

Filming began on Monday and Bowie has already shot his episode in which he sings.

While a BBC spokeswoman confirmed the names of those who are appearing in the second series, she would not comment on details of the scripts.

Gervais and his writing partner Stephen Merchant make changes to the scripts as they go along.

The episode featuring Bowie is believed to show the artist behind hits such as "Rebel Rebel" and "Diamond Dogs" bursting into song, prompting the ejection of Millman from the VIP area of a private members club, which he has bribed his way into.

Such is the appeal of the show that Madonna asked Gervais at last year's Live 8 concert whether she could take part.

The singer had to pull out owing to a clash with her world tour.

It helps that Gervais is a well-known name in the US, where his hit comedy The Office won two Golden Globes and was remade for an American audience.

In each episode of the sitcom, Millman turns up as an extra to the set of a different film, but despite his best efforts speaking parts continue to elude him.

Ashley Jensen, who plays his best friend Maggie, has won two British comedy awards for her part in the sitcom.

Merchant, who only made a brief appearance in The Office, has a beefed up role as Millman's utterly useless agent.

Stars who volunteer to appear in the show have to resign themselves to being sent up.

Les Dennis sportingly played himself as an actor being cuckolded by a younger woman, while Kate Winslet was happy to play herself as a foul-mouthed actress with a prurient obsession with sex.

Other story lines are believed to include Daniel Radcliffe, who plays the schoolboy wizard in the Harry Potter films, as a teenage yob and Orlando Bloom propositioning Maggie and being rejected.

- INDEPENDENT