Lady Elspeth (left) is in Brighton with husband Sir Menzies

Lady Elspeth spied Nick Clegg - the man at the centre the speculation despite his repeated vows of loyalty - walking on the seafront at Brighton.

"I don't know if you're being helpful or not," said Lady Elspeth.

"I'm trying to be," replied Mr Clegg, who says he would consider a leadership bid after Sir Menzies steps down.

Sir Menzies then stepped in to defend Mr Clegg, saying: "He's being very helpful."

Lady Campbell then completed the exchange - captured by ITV News cameras - by lamenting: "It's so tough."

Future leaders

The meeting came during a Lib Dem conference at which the future of Sir Menzies has been discussed across the media.

Mr Clegg and the party's environment spokesman, Chris Huhne, have been the names most often mentioned as future leaders.

Asked at a fringe meeting on Tuesday to state his intentions, Mr Clegg said: "If you are asking me would I stand against Ming, the answer is no".

When pushed on the issue, he responded that "if there was a vacancy in the future then I probably would".

This sparked a flurry of speculation about the leadership - prompting Mr Clegg to stress his loyalty to Sir Menzies.

'Totally relaxed'

Mr Huhne said: "There is no vacancy and it would be premature to even talk about the possibility as there is no vacancy.

"I am not a sort of Michael Heseltine figure who plans their route map to Downing Street from the day they come out of nappies. I wait for opportunities and decide at the time."

Sir Menzies told the BBC: "I like ambition. I am totally relaxed."

Answering questions e-mailed in by BBC News viewers, Sir Menzies said: "I am going to lead the party through this Parliament, through the next general election and into the next Parliament."

Sir Menzies - who is due to deliver a major set piece speech to delegates on Thursday - said he wanted to send delegates home "with a spring in their step" and "make it clear we have the policies necessary to change political face of Britain".