Still live: Bob Zimmerframe]

Through the flaring lights it was possible to see the double chins waver as the famously doleful face bent to the microphone.

Now you would not think it to look at him

But he was famous long ago

For playing the electric violin

On Desolation Row

Behind me a woman stared through binoculars. 'You can see all the wrinkles,' she said. 'Well, I suppose we've all got them now.'

At the bar before Thursday's performance there had been much discussion as to why, at 51, Bob Dylan still puts himself through live shows. There is certainly no flicker on that lined countenance to suggest that he enjoys them. The critics have been less than enthusiastic for some time. This week the Times critic asked: 'How is it possible to play the harmonica professionally for 30 years and still show no signs of improvement?' Last year a Washington Post correspondent went so for as to suggest, at the time of Dylan's Madison Square Garden concert, euthanasia.

Even his devout followers - and the Hammersmith Apollo has been packed out all week with them - admit that their hero, seen live, has some flaws. 'He can be halfway through your favourite song until you realise which one it is,' said Marcos September, a 21- year-old convert, a statement which was confirmed halfway through that night's concert when two Dylan devotees gave me two different titles for the song he was then singing.

Michael Stanhope, a teacher in higher education, said he had been listening to Dylan since he was a student at Newcastle University in 1966. He has all his albums, bar one, including the recent releases. 'There's usually two or three great tracks on each album,' he said. 'I just love him.' But even he, when I said I hoped he would enjoy the evening, said sadly: 'I probably won't. I haven't enjoyed him for ages.'

Still, when the singer appeared, the whole audience in the front stalls rose to its feet and began to sway to and fro to Dylan's lugubrious notes like so many snakes before a charmer.

It is possible, of course, that this charm partly resides in a kind of mutual masochism: that Dylan enjoys singing 'such depressing songs . . . they're nothin' but the unwinding of my happiness' (as he wrote in 11 Outlined Epitaphs) and that the audience enjoys hearing him suffer.

'I think he's a poet,' said Paul Curinarski, 29, standing in the lobby, wearing, with his Levis, a mock 18th-century sailor's hat and a single ear-ring. 'I've read William Blake and the beat poets, but Dylan's more relevant. I feel the pain in his songs.' If his hero were to feel some more pain, he thought, he might regain his creative spark. He was talking to Sue Austin, 26, who appeared to confirm a masochist trend among the Dylanites.

'I had a friend who was a dope smoker who ended in a lunatic asylum,' she said. 'He used to play Highway 61 all the time. At first I thought, 'Get this whining off]' But when he left I went and bought the album.'

On Sunday night, depression, if not pain, had seemed to be evident. Not until half way through did Dylan begin to sing with any emotion. Watching him picking up his harmonica, to a roar from the crowd, I felt a surge of pity for him, as he were an ageing circus elephant, condemned for ever to play old demeaning tricks to please the crowd. How must it feel to know that most people believe your best creative period was more than 20 years ago? The loudest applause, of course, came for the Sixties songs. When he sang:

Your old road is

Rapidly agein'

Please get out of the new one

If you can't lend your hand

For the times they are a-changin'

it seemed sadly apposite, particularly when, on 'It's Alright Ma (I'm Only Bleeding)', he stumbled and stopped altogether. 'Go on, Bob] Go on]' men in the crowd cried, raucous and mournful, like geese on the wing, as though Bob needed the sympathy and support of the masses below to keep going. But by Thursday his mood seemed to have changed. He sang from the start with much more conviction, and kept the pace going, bowing as uproar greeted the end of each song.

For the times may be changing in his favour. There were many teenagers in the audience, drawn, they said, more by the music than the current Sixties revival.

'Music now,' said Patrick Harte, 18, 'is drivel. There's no soul in it.'

'Yeah, my Dad listened to Dylan,' said his friend Haley Ottaway, also 18. 'But it doesn't put me off.'

Marionne Juanette, 25, was wearing a floppy mock Sixties hat and pink fun fur coat. 'I didn't like him at first,' she said. 'All that whingeing. Then you hear the lyrics. They're brilliant. I can dig where he's coming from.'

By the bar two members of the Sixties generation were contemplating the revival of Dylan's music among the young of the Nineties with something approaching complacency. 'I tell you, it makes your generation's taste in music valid,' said one of them, a dental surgeon. 'When I first heard it, wham] It's the most amazing thing I'd ever come across - just poetry. And now, your kids listen to Bob Dylan and say, 'We agree with you'.'

It is the poetry and the emotion behind it that make Dylan so beloved. The words are so muffled and droned in his live performances that the songs are almost as incomprehensible as opera in a strange language. It does not matter to his audiences, who have the words inside them: they are visibly in mystical communication with Bob, on his bad days or his good ones. What do the critics matter? Who cares for journalists? Not the man on the stage. As he wrote in 11 Outlined Epitaphs:

No, I shall not co-operate with reporters' whims . . .

who have no way of knowin'

that I 'expose' myself

every time I step out

on the stage.

Nic McAndrew, a busker, had come to hear him play. 'He's a genius,' he said. 'People like Wordsworth, you're force fed and you don't understand. This guy says it plain. If you think about it, he's a busker of genius who got lucky.'

(Photograph omitted)