He laughs! He cries! He's really quite Frank!

Frank Dobson, what's he like? He enjoys a crude joke like the next man, but he's sensitive, too, and prone to tears. He's the face of New Labour in the London mayoral race, but it's a face that sports an Old Labour beard. And as for his policies for the capital: well, the only thing I'm sure he's sure about is that he's not going to abolish south London

Look, I didn't mean to make Frank Dobson cry. Honestly, I wouldn't. It's just not my style, if I have a style, which is by no means certain. I just happen to ask him whether he ever cries and he says yes, he does. He says he cried "during Mandela's speech to both houses of Parliament". He adds: "I think I've had a very privileged life. I've been to lots of sporting things and I've been to all sorts of artistic things... but listening to the great man making that speech was it as far as I am concerned..." And blow me if a little tear doesn't ooze out the corner of one eye and start trickling down his cheek.

Look, I didn't mean to make Frank Dobson cry. Honestly, I wouldn't. It's just not my style, if I have a style, which is by no means certain. I just happen to ask him whether he ever cries and he says yes, he does. He says he cried "during Mandela's speech to both houses of Parliament". He adds: "I think I've had a very privileged life. I've been to lots of sporting things and I've been to all sorts of artistic things... but listening to the great man making that speech was it as far as I am concerned..." And blow me if a little tear doesn't ooze out the corner of one eye and start trickling down his cheek.

He is embarrassed. He's from Yorkshire. He's the son of a railwayman. He's a former leader of Camden Council. He's a former cabinet minister, a former secretary for Health. He's meant, too, to be Old Labour, a bit of rough, not some New Labour big girl's blouse. He says: "Bloody hell, you've upset me." He is annoyed that the photographer is still clicking. "Please, do not take a picture now!"

I am mortified. I try to reassure him. I say, don't worry about it, Frank. We all cry. I cry. I cry whenever I have to go to south London, in fact. It's horrible. It's revolting. It's full of enormous, perplexing roundabouts, put there to flummox and confuse those foolish enough to attempt any of the bridges. And it's got Penge. Penge! It sounds like something your cat could die of. "Yes, I had to put poor Kitty down. She had Penge, and was suffering so." If, Frank, you get to be mayor of London, could you perhaps abolish south London? You don't have to blow it up. You could just move it somewhere else, maybe to Peru. Then, perhaps, you could shift the Thames and expand north London for north Londoners, that literate and sophisticated populace to whom the capital rightly belongs?

Mr Dobson dries his tears. He's a portly man with thick, sausagey fingers who, on the whole, looks like a prosperous and well-fed butcher ("Eee oop, missus, we've got some grand pork belly in today..."). He also has a big laugh and is big on laughing. He is bigger on laughing than weeping, as a rule, I think. Thankfully, he laughs a big laugh now. He says he understands about Londoners thinking their own particular patch is it, but no, he doesn't think he'll be able to help. "My son and grandson live in south London." I can see they might be more easily visitable there than in Peru ­ maybe ­ but still feel sorely disappointed. I think I may have to give my support to a Mr Kenneth Livingstone who, by the way, writes for this very newspaper, and might very well put a newt down my back in the lift one day were I to say otherwise.

Mr Dobson, however, has no such fears. Mr Dobson has recovered from his little weep. Mr Dobson is now squarely back on the campaign trail. Mr Dobson thinks Ken would be fantastically bad for London. Mr Dobson thinks Ken is ill equipped to co-operate. Mr Dobson thinks the Tories would in fact prefer Ken to Jeffrey Archer, because he would make "a better leader of the Opposition!" Mr Dobson thinks, ultimately, that any abiding affection for Ken is hopelessly misplaced: "I've no objection to someone liking someone, but I do think he would be quite unsuitable as mayor... I'm sure he wants to do right by London, but I also think he wants to find himself a prominent position from which to sound off about everything. I mean, I think London has enough problems without having its own foreign policy, defence policy, macro-economic policy, Irish policy..."

You wouldn't consider just blocking up the bridges? No, he thinks not. "I do have to go there."

Yes, this mayoral business is heating up juicily. And, yes, Dobson will probably become Labour's candidate. But will it represent a fair victory? Certainly, the Government desperately want him and, to this end, has imposed an electoral college voting system that does seem to swing things excessively in his favour. He was also given access to the names and addresses of the 68,000 members of the Labour Party in London, to whom he wrote asking for their support. "Unfair!" cried Ken. Dobson, however, thinks it a fuss about nothing. He says the list came from sympathetic MPs and MEPs, not from Millbank. It was not favouritism. At least this is what I think he means when he says: "What some people did not understand was that if the party gives the list of the London membership to MEPs and MPs, then that list comes from the centre, and will look like the official list, because it is the official list." Whether this will get him off the hook with the Data Protection Registrar ­ who is currently investigating ­ is, of course, another matter entirely.

Anyway, we meet at his campaign headquarters, near the British Museum, north of the Thames, which is an attractive and cosmopolitan area full of magnificent things like the British Museum, unlike south London, which is not, and only has "Upper Norbury". I'm rather early, so chat a while with the various volunteers and researchers in the office. Apparently, Matthew Freud ­ the PR whiz who currently does for Chris Evans and Geri Halliwell ­ has just come on board the campaign. Will this mean, I wonder, that a high-profile romance will have to be engineered for Frank if he is to reach number one? If so, who would the likeliest candidates be? We have a good discussion about this. Oona King would be the most photogenic, we decide, but a fling with, say, Ann Widdecombe would certainly arrest more front pages. I put the choice to him when he arrives. He says: "I've been having a high-profile romance for 32 years." He is known to be fond of his wife, Janet, with whom he has three grown-up children, and with whom he lives just up the road. He thinks, though, he might make a good Spice Girl. "I could be Fatty Spice... ha, ha!"

He does seem, on the whole, very good-natured. He can be nicely self-deprecating, too. Yes, he has extravagances. He likes the opera. He likes good hotels. But clothes? No. "I do not think my clothes-horse capacity would justify spending a great deal on cladding ­ ha, ha!" He is keen to be matey. Indeed, I've been told he likes jokes, that he is a great joke-teller. Tell us a joke, Frank, I say. OK, he says. "A Scotsman goes into a pub in Glasgow where the special offer is a pint, a pie and a fuck for a pound. The Scotsman orders a pint of bitter. "Aren't you interested in our special offer of a pint, a pie and a fuck for just one pound?" asks the landlord. The Scotsman thinks about it, then says: "Whose pies are they?'"

We both laugh our laughs: his that big, Yorkshire one, mine an attractive, dainty, interestinglycosmopolitan north London one. He has quite a naughty, un-Blairite vocabulary. He is known for this. It may, in fact, be something he rather hides behind, like the beard. It is so reassuringly Old Labour. But, truly, is he?

We move into a little side-room with some kind of assistant, who tapes the proceedings. For some reason we start off discussing tea, which leads me to ask him whether he thinks the round tea-bag really represents a significant step forward. At this point the assistant interrupts with: "You'd better get cracking, you've only got an hour." I say, pathetically, I am cracking, actually. Frank exclaims, shocked: "An hour! Good lord!" My confidence is rather shattered. Both are now looking at me expectantly. I had wanted to go on to the pyramid tea-bag, but now feel rather silly. I panic. I say: "So, Frank, why do you want to be mayor?"

I suppose, now, this did have to be asked but, even so, I regretted it almost instantly. His spiel goes on for ever. His spiel is something that you could happily have a nap to, and do. His spiel goes: "It's an enormous opportunity... it's almost impossible to exaggerate the difference between the mayor and any other politician there has ever been... five million people will have a vote!... it's about trying to get London working together on the three or four things that need sorting out... reducing crime and disorder, getting more economic investment, retaining existing jobs, getting new jobs..." Zzzzzzz... got any more jokes, Frank? Thankfully, he has: "Holmes and Watson go camping and, in the middle of the first night, wake up. Holmes says to Watson: "Watson, what can you see?" Watson says: 'It's a terribly clear night, Holmes. I can see the Great Bear. And the Plough. What can you see, Holmes?" "Well, Watson," replies Holmes, "I can see some bastard has stolen our tent!" I am very taken with this joke, and Mr Dobson is very taken with it, too. "It's even clean!" he cries. Does Mr Blair enjoy your jokes, I ask. Yes, he replies. "He has a very good sense of humour, in fact."

It is popularly thought that Blair ­ having decided that Dobson had the best chance of seeing off Ken Livingstone ­ piled on the pressure until Dobson eventually agreed to stand. True? Absolutely not, he cries. "Mr Tony Blair never raised it with me, never asked me to do it, never twisted my arm." OK then, what about people close to Tony Blair? Hmm? "Well... yeah... I mean... attempted pressure... but I don't regard them as capable of applying pressure, quite frankly. I am stubborn, you see."

He would like, I think, to be seen as some kind of admirable, Old Labour cuckoo in the swish, New Labour nest. I doubt, however, whether this is entirely the case. He is possibly as ambitious a politician as any of them. I am not saying this makes him any less likeable. I am not saying he is not a man of genuine feeling. I'm not saying that his earlier tears were manufactured. They weren't, I'm sure. It's just that this may be worth bearing in mind. I later ask him whether he still feels like a Yorkshireman. There is the most uncomfortable, long pause. He is rather wishing, I think, that he had allowed me to continue on to the subject of pyramid tea-bags. He is in a pickle, he knows. If he says "yes", what will Londoners think? And if he says "no" ­ what treachery! Finally, he comes out with: "Only sort of."

This is not overwhelmingly impressive. It may, even, be only as impressive as Croydon.

Frank Dobson was born in Donnington, on York's outskirts. His father, James William Dobson, was a railwayman who had been known as "Willie" until he married Frank's mother, Irene. "My mother did not like that name, so he became Jim."

The household was political, yes. "I can remember, as clear as day, discovering, from a discussion my father was having with my mother, that Labour people were OK, Tories were not, and there were Liberals in between. I must have been seven or eight at the time."

Jim, sadly, died of kidney failure when Frank was 15. Consequently, "Irene never went to church again." Frank is very against death. "I have a rooted objection to it. If a Tory MP recovers from cancer, I always go and congratulate them and give them a big hug." That should set their recovery back nicely, I imagine.

He first, he thinks, came to London at 17. To see The Mousetrap? No, he says. Have you seen The Mousetrap, Frank? No, he says. You want to be mayor for London and you haven't seen The Mousetrap, I exclaim, aghast. "I tell you what," he says, "when I am mayor, everyone will be able to see The Mousetrap." This, I'm afraid, is as specific as he'll get when it comes to policy.

Anyway, he came to London to attend the LSE, from which he went on to work for the Central Electricity Generating Board and the Electricity Council before becoming a Camden councillor and then, from 1979, MP for Holborn and St Pancras. Last month, he ditched being secretary of state for Health in order to stand for Mayor.

So what if it all goes wrong, Frank? What if you fail? They can't take you back into the Cabinet, surely? Haven't you burned your bridges rather? Possibly, he says, but even if everything implodes, "I won't have died."

True enough. You can't die of political failure. I imagine, though, that you could die of boredom in ­ let's say ­ Sydenham. It might, even, be frighteningly easy.