He makes his way down the winding stairway that leads to the canal towpath. Those stairs always remind him of the scene in 'The Christmas Invasion' where the tenth Doctor is selecting his new clothes. There was a spiral staircase in that scene. Today is no exception. Yet perhaps today, there is magic in the air. Or maybe melancholy. The sun, glaring down onto the still waters, transforms the canal into a giant screen that plays as he walks along the towpath.

He sees an excited seven year-old boy sitting in front of a television, watching the first part of 'The Daleks Invasion of Earth'. "Those aren't the Daleks. They're men taken over by the Daleks," he explains to his patient parents, every time a Roboman appears. Every single time. Then at last, gliding from the waters of the Thames, "THAT'S a Dalek!" Then the indignant fury as the theme music cuts in.

He sees himself in the playground with his three friends who together form the Tardis crew in their make-believe games. (The Tardis was a doorway with a light switch. When the switch was up the Tardis was in flight. When you wanted to land the switch was flicked down and the assembled group croaked out a raucous materialisation noise). His friend John summed up the feelings of the group when he declared; "I like the new Doctor but I prefer the old one." The group nodded sagely and then went off to face hordes of imaginary ants smothering the Tardis, under the control of the evil Zarbi!

He sees classic after classic, monsters after monsters, culminating in the joy of 'Evil of the Daleks", Surely the eighth wonder of the world!

He sees the Doctor spin away, "Stop it. You're making me giddy!" Suddenly Dr Who is in colour. All shiny and new and grown-up. The man in the velvet jacket and ruffled shirt is exiled to Earth. And he's got a job. Frustration mounts as the Doctor fails to get the Tardis working. Then, suddenly, without warning, the Tardis materialises half-way up a mountain on the planet Peladon and he's off again.

He sees the Doctor change into the curly-haired bohemian with a long scarf. Surely the gentlest regeneration ever! After a while it seems the Doctor was ALWAYS like this. As time goes on it seems that he always will be.

He sees his soon-to-be wife waiving him off on the railway platform as he departed for his first convention. Was he REALLY going to see 'An Unearthly Child' at last?

He sees himself turning on the radio one morning to find out who had been elected as President of the USA. Instead he was greeted by the news that Peter Davison was to be the next Dr Who. Peter Davison? Tristan from 'All Creatures Great and Small'? But he's too young, surely? Nevertheless, for the next few weeks he finds himself whistling the 'All Creatures' theme tune. He still does, sometimes.

He sees a clown in a sick-inducing harlequin coat trying to strangle his assistant in the Tardis. It's the most shocking scene in the programme to date. But he is soon gone.

He sees himself taking his two sons to see Dr Who on stage. The man in the velvet jacket and frilly shirt is back fighting Daleks AND Cybermen., whilst stagehands dressed in black whirl around him. The Ultimate Adventure.

He sees an end of pier comedian fall clumsily down some steps and play the spoons. He wonders whether he is watching the right program. The wonderful counterpoint of 'Remembrance of the Daleks' reminds him that he is. Then the show has gone, apparently for good.

He sees the books but they're not 'real' Dr Who.

He sees himself rushing home with a VHS of 'Dr Who – The Movie' and his family gathered around to watch. A false dawn. But it gave him one thing to hold on to. A marvelous eighth Doctor.

He sees another wilderness, filled with magazines, books, audio tapes...

Then, unbelievably, he sees a blond girl running into the Tardis, after a skinhead in a leather jacket. He ran alongside her, as did millions of others.

Barely a week later he makes a telephone call home from his New York hotel room to discover that he will only have him for another twelve episodes. But what a series! The sheer joy of the climax to 'The Doctor Dances' - "Everybody Lives!" - except the ninth Doctor doesn't.

He sees the tenth Doctor everywhere. In shop windows, supermarkets, on billboards. He's everybody's Doctor now. Those who kept the faith have to share him thinly.

And now, on the distant horizon, he sees the eleventh. At 26 years-old the actor is younger than his own sons! That should make him feel his age, but it doesn't. What will he wear? How will he sound? What will he say? Where will he go? As he ponders all these questions he feels like a seven year-old boy again. Perhaps that is the secret. That is why this creaky old show seized his imagination and remained a binding thread throughout his life.

When the Doctor regenerates perhaps, for a short while, we all do too.

He has reached the first bridge of the canal and passes under it. Emerging the other side he finds that the sun has gone in. The sky is overcast. The water is a grey-green sludge. The screen is blank. He sees the empty plastic bottles and other detritus littering the place. The towpath is a treacherous strip of mud. The magic has gone or is it the melancholy?

Alone again, he walks the canal.