By Tim Donovan
Political correspondent, BBC London, Lib Dem conference
Brian Paddick has said he is relieved to have joined the Lib Dem ranks after a career in the "authoritarian" police.
Mr Paddick was a senior Metropolitan Police officer
The former Metropolitan police deputy assistant commissioner said he had been "a police officer working undercover - as an undercover Liberal Democrat".
Mr Paddick is one of three Lib Dems vying for the chance to take on Ken Livingstone in May's London elections.
Barrister Chamali Fernando and former deputy party president Fiyaz Mughal also spoke at the mayoral hustings.
Speaking at a party conference fringe event in Brighton, Mr Paddick attacked the targeting of stop and search on people from ethnic minorities, and said police officers, not community support officers should be deployed in London's difficult inner city areas.
But in an attempt to show he was not a "one-trick pony", whose experience was confined to fighting crime, Paddick said he had "generic" skills which he would bring to bear on the capital's problems.
Promising to be firm but consultative, he pledged to seek a no-strike agreement with the RMT tube union which brought chaos to London commuters earlier this month with a stoppage by maintenance staff.
As a police commander in the borough of Lambeth, Mr Paddick pioneered a controversial approach to drug enforcement, directing officers to concentrate less on policing minor offences of cannabis possession and more on harder drugs.
It was a shift in thinking which helped pave the way for the reclassification of cannabis from class B to C.
His profile has remained high, because of his unhappiness with Sir Ian Blair's handling of the fall-out from the shooting of Jean Charles de Menezes at Stockwell tube station in 2005.
He said the Liberal democrats needed someone with that profile to "help put Liberal Democrat polices on the map".
"A lot of the policies are brilliant, but no-one knows about them," he said.
Earlier Mr Paddick told the conference he was opposed to ID cards saying they would be 'as much use defeating gun crime as they would have been at stopping the London bombings in 2005 - useless.'
The former police officer is favourite to win through against two far less well-known rivals.
Chamali Fernando said she was the 'fresh, young, unspun' candidate who could reach out to young Londoners who don't presently have a voice. "Ken and Boris will be like Punch and Judy," she said.
"I will be a rose between two thorns. Boris Johnson only decided to enter the race because Channel Four cancelled next year's Celebrity Big Brother."
A call for less gesture politics and more genuine commitment to creating social cohesion in the capital came from Fiyaz Mughal, the third short-listed candidate.
'The core belief of our party is inclusion, and we must fight attacks on our civil liberties.' He would make the mayor more accountable and transparent.
The result of a ballot of Lib Dem members will be announced in November.