The new Speaker: runners and riders

Contenders line up to succeed Betty Boothroyd

The race to replace Betty Boothroyd as Speaker promises many twists and turns before her successor is chosen in October.

Convention suggests she should be replaced by a Conservative but there are some strong Labour and Liberal Democrat contenders in what promises to be a long and fascinating election campaign.

William Hill's latest odds, 8 August

Michael Martin 8-11

Sir George Young 3-1

Sir Alan Haselhurst 4-1

John McWilliam 9-2

Menzies Campbell 9-2

Gwyneth Dunwoody 8-1

Sir Patrick Cormack 12-1

Michael Lord 20-1

Nicholas Winterton 25-1

Richard Shepherd 25-1

Tony Benn 100-1

Michael Martin The Glasgow Springburn MP and deputy Speaker has emerged as the favourite.

At one stage in July the bookies temporarily closed betting as a result of large sums being placed on the Labour MP.

Although he appears a popular choice, his candidacy may suffer from English backbenchers being unwilling to back a Scottish speaker post devolution.

Sir George Young The Tory shadow leader of the House has yet to declare his candidacy, but he could prove a strong contender.

He is respected across the House and convention favours a Conservative as the next Speaker.

John McWilliam Another MP with a reputation for independence.

He is the Labour chairman of committees and has said he would allow women MPs to breast feed in a side room away from the main chamber. The current Speaker ruled out allowing breast feeding in the Commons chamber or committee rooms.

Sir Alan Haselhurst An early favourite and a deputy Speaker, Sir Alan is one of the strong Conservative challengers for the job.

But if he runs alongside the other Tory deputy speaker, Michael Lord, they could run the risk of splitting the Tory vote.

Menzies Campbell The Liberal Democrat foreign affairs spokesman is said to be the preferred choice of the prime minister, but it is an endorsement which may do little to help his case.

If he were to win the post he would be the first Liberal to sit in the Speaker's chair since 1928.

Gynweth Dunwoody The Labour MP for Crewe and Nantwich was one of the first to throw her hat into the ring. She is a close friend of Miss Boothroyd, and has won respect from all sides of the House as a tough questioner on the Commons Environment, Transport and Regional Affairs Committee, which she chairs.

The independently-minded Mrs Dunwoody has been critical of government policy, and has been particularly damning of the John Prescott's plans to part-privatise air traffic control.

Sir Patrick Cormack The Tory MP was, up until 21 July, Sir George Young's deputy on the Tory frontbench, until he stepped down to launch his bid for the speakership.

Sir Patrick says he has cross-party backing for his bid.

Michael Lord Another Tory deputy speaker, seen as quiet but commanding, and a safe pair of hands.

He was been in the position since 1997 and has strong anti-EU views.

Nicholas Winterton The Tory right-winger is well known for his independence, a key qualification for the job.

He is also one of the few MPs to come out and say publicly that he is actually running for the post.

The Macclesfield MP also has experience in chairing debates in Westminster Hall, the overspill chamber for the Commons.

Richard Shepherd A respected Tory backbencher with a strong reputation for defending the rights of Parliament, and a passion for freedom of information.

It remains to be seen whether he will enter the race.

Tony Benn A veteran parliamentarian respected as such across the House, Mr Benn's name entered the frame only recently.

But the Chesterfield MP and former cabinet minister has been urged to run by a number of Tory and Labour backbenchers. Mark Seddon, editor of the left-wing Labour weekly Tribune, is among those who have called on him to stand.

But last year Mr Benn announced his intention to stand down at the next election. He has recently insisted he is not seeking to become Speaker.

Instead he intends to use the media speculation to mount "a serious campaign to get the House of Commons to accept the reality that it is being progressively sidelined".