Ken Buchanan bounces about the ring shadow-boxing, throwing lefts and rights at an imaginary opponent.

He is lithe and quick and light on his toes and, in one swift movement, his right knee bends, he shifts his weight and a rib-breaker of an uppercut is followed by a crashing right hook.

He ducks again and moves backwards, keeping his hands high to protect his chin, and, as he bobs and weaves, he moves forward punching rapidly - a routine that lasts until a bell rings and he drops his hands and jogs towards the corner.

"I'm 100 per cent convinced I could take on some of the young lads who are boxing today," is the first thing Buchanan says in a thick Edinburgh accent before swigging water from a plastic bottle.

"I mean it. I am nearly the same weight now as I was when I won my world title in 1970."

At 66 years old - a pensioner - Buchanan qualifies for a free bus pass from the Scottish Government, but the former lightweight boxing champion of the world remains as fit as the proverbial fiddle.

Remarkably, for a man fast approaching his seventies, he is hardly out of breath and, after resting for barely a minute, he steps back into the ring to box again, his strapped wrists a blur as they punch air for the duration of another bout.

This is the man who - according to some sporting commentators - was arguably the greatest pound-for-pound boxer ever to come out of Britain. Indeed, Buchanan is the only living British fighter to be inducted into the International Boxing Hall of Fame and, in 1978, he was voted Greatest Ever British Boxer in a poll organised by the sport's trade newspaper, Boxing News.

Undisputed champion of the world until he lost controversially to the legendary Roberto Duran in 1972, Buchanan fought 69 professional fights during his career, 64 of which took place "away from home" - an extraordinary feat for a boxer.

It was on a balmy afternoon in San Juan, Puerto Rico, on September 26, 1970, that Buchanan beat world lightweight champion, Ismael Laguna, to take the WBA title.

He recalls that day well, but despite the fact he should be reminiscing by the fire about events some 40 years ago, Buchanan announced on television recently - to much astonishment in Scotland - that he would like to fight again.

"I spar regularly and I know I could fight again," he says when training is finished.

Buchanan is talking about unlicensed fights, or "white-collar" boxing, as opposed to regulated bouts, because he knows that someone his age would never be granted a licence by the boxing authorities. His words have provoked some debate and a collective response from fans and friends that he should drop the idea immediately.

It is not the first time Buchanan has announced a desire to come out of retirement, having proposed the notion three years ago when he was short of money for a legal battle.

Around the same time there were reports he was selling his coveted boxing prizes - a Lonsdale belt won as British champion in 1968 and his world title belts from the 1970s in Puerto Rico, but Buchanan says they were untrue, that his life is on track again after well-documented alcohol problems and that he is in prime condition both mentally and physically.

"I've gone through some rough times but come out the other end. I just want to keep boxing. That's all."

Buchanan spars and trains at least three times a week at Lochend Amateur Boxing Club, a 10-minute drive from his home in Leith, Edinburgh. The hall where he sweats is a treasure trove of boxing memorabilia.

On one wall there is a picture of Mike Tyson wearing a Scotland football shirt, on another, a pair of sparkling turquoise shorts, framed and gifted to the club by the brilliant but flawed Ricky "The Hit Man" Hatton.

There is a raft of black-and-white photographs of legends such as Manny Pacquiao and Muhammad Ali, plus pictures of Buchanan in his heyday, including one of him sporting tartan shorts while fighting fellow Scots boxer Jim Watt, when he defeated his rival for the British lightweight title in 1973.

Buchanan is a gregarious man who could talk for Scotland, and he rattles off anecdotes about his career and the friendships he has with the likes of former British boxing champs John Conteh and Alan Minter, as well as Roberto Duran, his Panamanian nemesis who defeated him in 1972 at Madison Square Gardens, New York, in dubious circumstances.

"It was a knee to the groin in the 13th round and Roberto should have been disqualified," Buchanan says. "It does keep going round and round in my head after all these years, but he later said that I was his toughest-ever opponent in boxing and today we are good friends."

He simply adores boxing and still travels Britain speaking at sporting dinners, which affords him the opportunity to spend time with ex-champs and household names such as Mike Tyson, whom he is also friendly with.

It was another black boxer famous some 60 years ago who pricked Buchanan's interest in the sport as a young boy. At the age of 8, he joined the Sparta Boxing Club in Edinburgh - lying about his age in doing so - after seeing the Joe Louis film The Brown Bomber with his father, Tommy, now 97, who became his son's right-hand man throughout his subsequent career - despite having never boxed himself.

Buchanan won his first senior title at the age of 17, taking the East District bantamweight championship. That success was followed in 1965 by the Scottish and ABA titles and, after 23 fights and 23 wins, he knocked out Maurice Cullen in 1968 to become British Lightweight Champion.

He was eventually given a shot at the world title in 1970 and beat Laguna. Despite Buchanan's magnificent achievement, only six people turned up at Edinburgh Airport to celebrate his triumphant return from Costa Rica. Four of those people - his wife, Carol, his son, Mark, and his parents-in-law - were relatives.

After becoming undisputed world champ in 1971, Edinburgh offered some redress by providing an open-top bus that toured the city.

In 1970, he won the American Boxing Writers' Association's Fighter of the Year, beating superstars Muhammad Ali and Joe Frazier. He also topped the bill seven times at the world's most prestigious boxing venue - Madison Square Gardens, New York - a record for any European boxer.

A film to be released in early 2012 - The Boxer from Somewhere Else - will document his life.

"It's not quite finished yet, but I'm looking forward to seeing it," he says.

Buchanan also talks about his latest role as honorary president of Scotland's newest boxing club, West End Boys, in Dundee. The club was started by two former gang members following a spate of drug-related deaths, and Buchanan was approached for help.

"These two guys are doing a good thing by getting kids off the street. There is too much gang trouble these days. We had fights when we were kids, but it was none of this nonsense about using weapons. It was a square go with fists and that was that.

"I guess I've always been fighting and I'll go on boxing as long as I can."