Pure bloody-minded determination

It's a Tuesday morning in the city of London , and we're all milling around on a pavement outside Marks & Spencer, awaiting the arrival of a legend. It's a strange old scene. Puzzled commuters are veering off the kerb to negotiate an army of fluorescent-jacketed volunteers; dignitaries are mingling with celebrities who are mingling with curious M&S shop assistants, and a four-piece New Orleans Jazz Band are filling the idle minutes before kick-off. After nine days, 17 cities and nearly 200 miles, Ian Botham is about to embark on the final leg of his 11th charity walk.

As celebrity appearances go, the scene is ordinary almost to the point of anonymity. Twenty-one years have elapsed since Beefy - inspired by a group of terminally-ill children he met at a hospice in 1977 - first pulled on his walking boots and set out on a one-man mission to crush the terrible blood disease of Leukaemia. Seven thousand miles later, and more than £8 million to the good, what hype there once was has evaporated, and all that remains is pure, distilled, bloody-minded determination.

The thrill of the chase has undoubtedly spurred him on. "When we did the first walk from John O'Groats to Land's End in 1985," says his Beefiness, "there was a 20 percent survival-rate for people with leukaemia. Now that's up to 80 percent and I won't stop walking until it's 100 percent. If we can beat one form of cancer, who knows what doors that'll open." It is the great competitor's greatest challenge, and now, at the age of 50, he has absolutely no intention of slowing down with the finish line so near.

By 10.50am, Beefy is standing next to a makeshift podium on Finsbury Pavement, doggedly running through an array of limbering-up exercises. It is the sort of ritual I swear I never saw him bother with in his days on the cricket pitch - a concession, perhaps, to his advancing years? Perhaps not. He's still going about his business with the intensity of an athlete, and besides, I've heard legendary tales about his approach to days such as this.

So, too, have his mates who've come along for the ride. Where once he would march elephants across the Alps, now Botham merely thumbs through his directory of drinking buddies, and subjects them to a beasting they will never forget. "Beefy told me just to pitch up at M&S, be there before 11, and we'd go for a little walk," explained the South African golfer Ernie Els, one of six head-turning additions to this peculiar pavement melee.

Piers Morgan, Botham's former editor at The Mirror, is another with his walking boots on. Having spent the past ten years pleading a host of prior engagements, he has finally run out of excuses to dodge the draft, and within seconds of the start, he is already running to keep up. Botham seems sadistically proud. "I can assure you, the rest of the body might be creaking, but that's the one thing that's stayed the same. It's just a natural walking pace, sadly for all my friends that come and join me!"

Whatever the pace is, it is blistering and ever so slightly surreal. The scenes in the first 100 yards are nothing short of a breach of the peace, as the entourage strides along the streets of Central London, with police outriders halting the traffic at every corner and gawping bystanders giving it the old "it's ... err ... thingummy ..." look, while simultaneously pouring their small-change into the passing buckets.

Botham is steaming along now, shades wrapped around his features and red cap pulled down low, with his mates four-abreast alongside him, determined not to break stride. As well as Els, there's Barry McGuigan, the former World Featherweight champion (whose own daughter fought and overcame Leukaemia); Daley Thompson, the former Olympic decathlete, whose feet apparently were so badly blistered on an earlier leg that he had to miss his two days of running in 20 years; and DJ Spoony of Strictly Come Dancing fame, who quips: "I'm only here because no-one under the age of 25 has ever heard of this lot."

And then, of course, there is the support cast - the bucket-wielders of Team Botham, most of whom have been with him since the very first trip in 1985. "They give up their time for nothing and turn this into a holiday event," says Botham, "but then they are mad." Like a pack of gun dogs, they seem to cover three miles to every one on the route, as they weave into the crowds and fill the coffers, tirelessly marshalled by his daughter, Sarah, who quit a high-profile job at Sky last year to devote herself to the logistics of this latest great trek.

And no small amount of planning has gone into this extraordinary final leg. As layers of clothing are shed - most of them by the toiling Morgan - the procession weaves past St Paul's, up through Holborn, around the Centre Point building, across Soho Square and out onto Oxford Street - the busiest road in London. And there it hits you. It takes some friends in high places to bring Britain's capital to a grinding halt, no matter how temporarily.

Suddenly, there's a carnival atmosphere up ahead of us, as the finish line draws closer. A pair of gold-jacketed drummers appear out of a side street, followed two blocks later by a trumpeter and a pair of jugglers. At Bond Street station a blue-suited stiltwalker wobbles into the fray and it's at this point Botham seems ever so slightly embarrassed by the fuss - or else he's frustrated that his brutal pace has been forced to slow down.

But, with upwards of £500,000 raised in the space of nine high-octane days, he is entitled at last to wind down and take stock. "This has gone, per mile, as well as any walk we've done," Botham concedes, as he greets the boxer, Michael Watson, at the finish-line - a man whose refusal to quit in his recovery from chronic brain-damage mirrors Beefy's quest to crush Leukaemia.

Naturally, he's far from done yet. "Next time, maybe we'll find 17 cities in the UK that we haven't done. Maybe in a year or two, we'll get something going." But has he ever, even once, considered slowing down? The question seems impertinent from the moment it is uttered.

"No?" he scoffs. "Why?"