SOME people call me the Space Cowboy, but only those who remember me with a 10-gallon hat after a similar amount of pints in the Maggie, a pub that supplied an illegal high by one simply breathing in the atmosphere.

But no one has ever called me the Gangster of Love or even the petty officer of heavy petting.

To cut the quick, I have never been cool. I was always been uncomfortably warm, more conventional, more Pearl and Dean than Jimmy Dean.

In truth, there are not that many cool characters around. There was the guy at secondary school who played football with his hands stuck out like balancing aerofoils who could not have seemed more effete if he was wearing a tutu and an Easter bonnet. But he did not care. And that was cool.

There is the retired greyhound at Saracen Cross. It is a regular treat for me on the road to work to catch him at his morning constitutional. He lopes up to the traffic lights, waits for the green man and the subsequent bleep, and crosses the road with the gait of the Pink Panther. Now that is cool.

But there are few cool sportsmen or women. They are plenty of brilliant, powerful, inspirational and dedicated sports stars. But cool? Lionel Messi has the aspect of the shy boy who has forgotten to do his homework. Cristiano Ronaldo is as naff as an Essex boy in a champagne bar. Roger Federer is as cool as a lounge singer on an all-inclusive cruise.

But once, back in the ice age of sport, everyone seemed cool, but no one was cooler that Johnny Unitas. His nickname was even cool: Johnny U. He was the - and I mean the - quarterback for the Baltimore Colts in the 1950s. He is also the subject of what may just be the best American Football book ever. Tom Callahan's biography of Unitas is a piercing glimpse at an era, a knowing stare at what constitutes greatness.

Johnny U was cool because he was tough, brilliant, a leader and capable of throwing a ball precisely in an era where quarter-backs where as protected as animals the royal family wants to shoot. He was also cool because he did not try to be cool, indeed he did not want to be cool. He wanted to be Johnny U. And that was a tough ask.

He would play with broken ribs, he would breathe in deeply, ignoring a punctured lung and throw the ball deep. He would call out plays through a mouth bloody and disfigured by the brutal application of an opponent's forearm or helmet.

But he won matches, he won praise from the fan and he won the respect of his team mates.

Tight end John Mackey was struck by dementia late in life, severely restricting his powers of recall. But he would often say: "I remember everything that I need to remember. Johnny Unitas was my quarter back."

Johnny U , with his buzz cut hair do and his angular face, was no matinee idol but he was a player whose innate strength, whose dedication to dragging his team to victory, was appreciated by anyone who watched him take a snap.

He had many footballing qualities but it was the personal ones that made him, unwittingly, cool. He was a sporting genius but he backed his talent with hard work. He was a faithful colleague but a demanding leader. Brutal behemoths in the huddle would quiver in shame and hurt when, after a missed block, Unitas would mutter quietly about the need for everyone to do their jobs.

He also backed his ability. He would go for the throw rather than the simple option of abdicating his brilliance to a kicker for safe points. Famously, he did this successfully in a championship game against the Giants in 1958, observing later without bombast: "Nothing against Myhra [the kicker], but I had more confidence in me."

But his coolness was heightened by a quick wittedness off the pitch. He had that serenity under pressure that allowed him to confound opponents not only by deed but by word.

Once, playing against Miami, he came up against a former team mate who had been discovered stealing from team mates in the Colts' locker room. Asked about whether the miscreant was a kleptomaniac, Bert Rechichar, the defensive back more noted for his belligerence than his intellectual brilliance, responded: "Kleptomanaic, hell! He's a f****** thief."

Johnny U was cooler. Walking on to the field, the thief, now playing on the opposition, warned him: "Not today, Johnny. Not this time, big fella."

Johnny U did not break stride but replied: "Do you still have my watch?"

Johnny U by Tom Callahan is published by Three Rivers Press