Brian Paddick calls it the Paddy Ashdown problem. How does a former policeman, used to rules, hierarchy and being obeyed, adapt to the free-flowing world of politics where you have to argue, not tell; persuade, not order? Like Ashdown, the former Special Boat Service officer-turned-Liberal Democrat leader, it is something Paddick (now attempting his second run at London Mayor) is still concerned about.
"I've come from a situation where people did what you asked them to do because you were in a disciplined organisation," the former Met Deputy Assistant Commissioner says.
"That is very different from having to encourage and cajole volunteers to support your campaign. The Met may not be the most professional and well-oiled machine, but political parties are very different in the way they operate. It was a bit of a culture shock, really."
That is apparent when we meet in his immaculately kept flat in Lambeth, where Paddick is preparing for his second mayoral hustings of the 2012 campaign to be held that evening by the business group London First.
He may now be a politician, but he still has the air of policeman. He carries himself ramrod-straight, and talks in sharp, direct sentences.
He admonishes an aide (only half-jokingly) for getting fingerprints on a glass vase as he moves it out of the way for The Independent's photographer.
Unlike his rivals "Ken and Boris", it is hard to see the electorate being on first-name terms with Brian.
In purely policy terms, it is hard to argue that Paddick is not qualified for the job. After transport, the most important part of the Mayor's role is providing political oversight of the Metropolitan Police, and Paddick has ample experience. A serving Metropolitan Police officer for more than 30 years, he started as a constable in Holloway and served variously in Lambeth, Fulham, Lewisham and Croydon, rising to Deputy Assistant Commissioner with responsibility for 20,000 officers.
He was also the highest-ranking UK police officer to be openly gay.
But anyone who thinks the Met would get an easy ride from a Mayor Paddick would be mistaken.
Take last summer's riots. He is in no doubt the police were partly responsible for them – for their response at the time, but also for failures which had built up over many years.
"Riots don't just happen. They happen against a background of underlying tension. I realised how bad things were when I was advising Nick Clegg's office about what he should put into his Scarman lecture.
"I suggested he say the relationship between the police and the black community was much better than in 1981, but the organisers suggested he take it out, otherwise he would be seen to be out of touch with his audience. That's a bit worrying.
"The police have never addressed the issue of disproportionality in stop-and-search. You are still four and a half times more likely to get stopped and searched if you are black than if you're white in London. A survey published yesterday found 25 per cent of Londoners don't believe the police are on their side. That's a significant proportion of people – two million people at least. So you've got that underlying tension."
Operationally he also believes mistakes were made. There were no senior officers on hand to meet the family of Mark Duggan (the young black man who was shot by police, sparking the initial disturbances). There were not sufficient officers on duty to deal with the trouble that broke out, and the tactic of not arresting looters led to more looting.
So how would Mayor Paddick improve things? He is critical of politicians' knowledge of policing, and believes that his experiences can make a difference.
"I went to a meeting of London MPs with the Commissioner and it struck me how appallingly badly informed politicians are about policing.
"They were asking the most naive questions... like why didn't the local senior officers get the officers kitted up in riot gear and take them out on the streets – that is a complete lack of understanding about how public-order policing works.
"How much more effective could the dialogue between the Mayor and the Commissioner be, if the Mayor knew what he was talking about? A commissioner could come to me and say, 'Brian, you know the situation, this is an effective way of dealing with it; is it possible to get the resources to do that?' I wouldn't need to get people who know about these things to do me a report. We talk the same language. It would be a more effective way of doing business."
Of course, Paddick does not want to be seen as only a law-and-order candidate, and his manifesto has interesting ideas on transport, housing, immigration and business.
On transport he proposes cheap fares for workers (many of them poorly paid) who travel on the Tube early in the morning, and hour-long bus tickets to allow travellers to change from bus to bus as you can do on the Tube.
In a dig at Boris Johnson and his new Routemaster buses, he adds: "If you don't spend money on cable cars across the Thames and on buses modelled on your own home with three entrances and two staircases, you will have more money to hold fares down without jeopardising the investment programme."
But despite answering questions frankly, there is something missing.
Paddick was hard to warm to. During our meeting, I felt like I was on the verge of getting a verbal dressing-down.
It was something his aides picked up on, too. And later that evening, after the hustings, they suggested we have another chat.
Paddick could not have been more different. Gone was the prickliness and the harsh stare. In its place was a smiling, joking (if still a little waspish) candidate.
So why the change? Was he nervous about the hustings?
"To be honest, I was concerned about the debate because at the previous one three weeks ago it was like the 'Boris Johnson admiration society'. I was concerned – not because I don't know my facts, but because last time I felt they were unreasonable in their admiration for Boris Johnson. This time I felt it was much fairer and more reasonable.
"People actually seemed to be listening and weighing things up on the merits. I was quite pleased about that."
He also says there was another reason.
"I don't see my husband very often because he lives in Oslo. He arrived about midnight last night and I had to throw him out on the streets because you were coming around.
"Last time, he took two months off to be with me during the campaign. This time, I said to him, 'Look, I'd rather we spent time together when the pressure of the campaign is not on. So today was difficult because I saw him for breakfast and I haven't seen him since and it's now more than 12 hours later."
Of course, with "Ken and Boris" this would never show. They are consummate performers able to turn charm on and off as needed.
Paddick cannot do this. Last time, his campaign was plagued by rumours of unhappiness. Staff said he treated them badly and didn't respect the efforts they put in on his behalf. Paddick believed he was not given enough support from Liberal Democrat headquarters.
This campaign is better resourced and, by all accounts, much more professional. Paddick feels he knows what to do this time, and is more confident taking on his opponents.
But clearly it doesn't always work. And he admits that.
"At the end of the day, and I know it's unusual in a politician, but I am sensitive. I care passionately about people – not just my partner – and I'm afraid I can't take the happy pill. What you see is what you get."
Mayoral election: The other contenders
Boris Johnson Conservative
Key issues: The incumbent mayor has made cutting waste at City Hall a key election pledge.
Ken Livingstone Labour
Key issues: Has promised a 7 per cent cut in transport fares; to reverse police cuts; and to restore the educational maintenance allowance.
Jenny Jones Green
Key issues: The London Assembly member has made opposing Government spending cuts a central part of her campaign.
Siobhan Benita Independent
Key issues: Has vowed to freeze transport fares until April 2014, with free travel for Londoners seeking work and reduced fares for students.