It's Boom time for Bob

Bob Geldof, to my surprise, is not grumpy at all - in fact, he's full of apologies. "Sorry, sorry, I'm late, but I almost didn't make it.'' He woke with a bad case of the flu, considered staying in bed but hated the idea of letting anyone down. There are interviews to do, a TV show to record; his life, as usual, doesn't stop for illness.

Despite feeling "the worst", he is utterly charming and still manages to talk non-stop with his trademark energy, enthusiasm and compassion. He may be famously irascible, grumpy and a bit of a bully in interviews but today he is simply, effortlessly, the smartest, most articulate pop star around.

"I've got too much on to take a sick day. I've got to do Bo' Selecta! (a bad-taste, late-night Channel 4 satirical comedy) this afternoon," he says, taking off his brown velvet coat, scarf and sunglasses before slumping onto a sofa at Soho House and ordering a pot of strong, black coffee. "I've never seen it myself; I'm doing it because the kids want me to do it."

Which is a bit of a turnaround for the Geldof clan. For, although Sir Bob is now 52, he is often the one who influences the popular culture choices of his four daughters - Fifi Trixibell, 20; Peaches, 13; Pixie, 10 and Tiger Lily, six - rather than the other way round. Sometimes it gets him into trouble. "I remember listening to Eminem for the first time in the car. I just went, f***! I kept going back and listening to the words, because I'm a words geezer. I gave it to Peaches and Pixie to listen to. And they really got it."

He laughs, pushing his well-cut grey hair off his face and undoing the buttons of his smart, brown pinstriped suit. "Finally they were listening to decent music. The boy band posters came down and the Eminem ones went up. For me the boy band drivel was like going back into Bay City Roller territory. Then the girls started writing essays defending Eminem at school and they got into trouble. I went to see the headmaster. I asked him if he had liked The Rolling Stones and if he'd got into trouble with his own father for doing so, which he had."

Geldof tried to explain that his daughters listening to Eminem's controversial opinions was only like the headmaster listening to the Stones or The Who when he was younger. "He kept saying: 'But Bob, it's the language.' But the language is fantastic! I didn't want to be Cool Dad but I wanted the headmaster to know that Eminem's attitude is no different to that sullen group of scruffy, deranged boys that were The Rolling Stones." Geldof may not want to be Cool Dad, but, then, there are many things he didn't set out to be.

He didn't aspire to be voted a Best Mum in an

Irish magazine survey. Yet, through no fault of his own, he is now, with the help of his French actress girlfriend, Jeanne Marine, bringing up his own three daughters - and one that isn't even his.When Paula Yates, his partner of 19 years and mother of his daughters, left him in 1995 for INXS singer Michael Hutchence, his three daughters moved in with him. And when Hutchence, and then Yates, tragically died, in 1997 and 2000 respectively, he immediately took in their daughter, Tiger Lily.

He didn't dream of saving the world, yet in 1984 he galvanised pop stars to record Do They Know It's Christmas? to raise money for the famine in Ethiopia and a year later went on to organise Live Aid, which raised £40 million.

He didn't want to be a pop-star spokesman, yet he campaigns against Third World debt and now for the rights of divorced fathers to get equal custody of their children.

So, does this reluctant hero see himself as some sort of saviour? "It's just the way I am, unfortunately. Once I start thinking about something, be it Third World debt or fathers' rights, I have to unravel it. It drives me mad and it exhausts me, but I have to get to the bottom of it."

The subject closest to his heart is that of fathers and their custody battles. Of course, writing his polemic, The Real Love That Dare Not Speak Its Name (a collection of highbrow essays reviewing the current legal system) has kept his own experiences alive. "I can remember very clearly how I felt when I was fighting for my own children: why am I not being listened to by the courts? It's nothing to do with this great woman (Yates) or these children that both of us love to death."

His children are clearly a huge source of inspiration and comfort to him, particularly during the darkest moments of his split with Yates and then her fatal drugs overdose. He said recently: "When the horror was at its worst you want to go to a grey, remote area of the world and howl into the void, but you can't because you have other responsibilities that are greater than your pain."

He sits forward on the sofa. His eyes are glistening. Even now, he still gets emotional about what happened. "Neither of us - Paula nor I - did anything wrong. She fell out of love with me. I was devastated. But why are my children then gone? What have I done? I don't mind coming to an accommodation. But who the f is the state to take my kids from me?" He coughs. "If it's happening to me, then it must be happening to others."

Simple humanity and painful personal experience aside, part of what has made Bob Geldof an enduring spokesman is his need to articulate what he feels. Even in his twenties, when he was frontman in The Boomtown Rats, he got into trouble in Ireland for writing controversial songs such as Banana Republic, which bluntly attacked his homeland for what he saw as its religious and political hypocrisy.

He thinks speaking his mind must run in the family. He recently took his daughters to Dublin, where he grew up, to visit his 89-year-old father, a retired travelling salesman who has just driven his camper van around Croatia on his own (Geldof 's mother died of a brain haemorrhage when he was seven). "We had lunch and all of us were fullon. My dad, my old aunt and uncle, my daughters - we never shut-up. We argue all the time," he laughs. "It seems to be the Geldof gene. The girls love to argue - I guess they're as passionate and driven as I am." But of all the hats he can choose from on any given day, Sir Bob says there is one he will always prefer: pop star. For Geldof, who has given so much to others, music is his saviour. "When I'm playing live, I feel most Bob Geldof-ish. Whatever madness is going on around me, there is a stillness when I'm on stage. If I do a good gig, I can sleep the sleep of the just."

He is cagey when I suggest that it stems from a need to stand on stage for approbation, having lost a parent early in life. "That may be true of people like John Lennon and Paul McCartney,'' he says. "For me it's an escape."

An escape from the everyday public persona of Bob Geldof the reluctant hero, the thing he loves doing best? "I don't know how to explain the way performing makes me feel. Perhaps the closest I can get is to say it feels like I'm at home on stage."

This month sees the release of The Best of The Boomtown Rats and Geldof has been thinking about the past more than usual.

For the first time, he has realised what a cool band he fronted. He has laughed at some of the lyrics: "Mary of the 4th Form was about me not being able to get a shag," he explains. "I've been thinking about how I tried to pull Mary Priest, now PA to the Irish prime minister."

He has also, inevitably, been reflecting on the artist as a young man. "I was really irritating. Seemingly full of myself. But then again, all the bands in that punk period were full of bombast. And you have to remember that we were up against the likes of John Travolta and Olivia Newton-John, who were at number one with Summer Nights till we knocked them off with Rat Trap."Bob Geldof - the driven fund- raiser, the petitioner for the Drop the Debt campaign, the spokesman for desperate dads, the entrepreneur, the grey-haired pop star - still somehow finds times to be a normal bloke.

"I used to think I'd grow old in the house I bought in Kent 20 years ago. But London is the most happening city on the planet and I can't imagine living anywhere else. I'm mad for it."

There is a glint in his eyes. "I'm going to be one of those old guys still having a cappuccino on the King's Road and watching the girls from Storm model agency passing by when I'm 80. I do it now. They're gorgeous."

The Best of the Boomtown Rats is out on 20 October. Bob Geldof will perform Boomtown Rats songs at the Union Chapel, Compton Avenue, N1, on 6 December (box office: 020 7395