Last night the world ended for Gary from Portsmouth. Gary, a shift-worker who spends his evenings printing explanatory leaflets for tampon packets, cannot believe what has happened.

'I'm gutted,' he said. 'I mean, how can the BBC do this to me? I feel . . . I feel completely disenfranchised.'

Every night Gary tunes in to BBC Radio 1, for the Bob Harris music show. For four years, it has carried Gary and 900,000 other assorted shift-workers, students and security guards through their nocturnal tasks, filling the hours between midnight and 4am with mellow music and whispered chat. But last night was the last time.

'As from tonight,' said Gary, 'the BBC is banned from my house.'

Next Tuesday, Matthew Bannister officially takes up his position as the new controller of Radio 1. Promising to be a new broom, Bannister's influence has already shot through Broadcasting House like a fierce vindaloo. Household voices such as Dave Lee-Travis, Simon Bates and Alan Freeman resigned in advance of his arrival; Nicky Campbell departed to spend more time with his wife. But the first thing the new man did concerned the broadcaster who fills more hours than any other Radio 1 employee: he sacked Bob Harris.

It seemed like a sound idea at the time. There was Radio 1, pilloried in the press as the Jurassic Park of broadcasting, employing as a principal disc jockey a man who was dismissed as a dinosaur as long ago as 1977 when Sid Vicious attacked him in a night-club, calling him a tired old hippy. What better way to signal your youthful intent than by axeing Whispering Bob, who became a household sobriquet presenting the television rock show The Old Grey Whistle Test so long ago that Labour was in power. After all, the man's even older than Janet Street-Porter.

'We had a five-minute chat during which he told me Radio 1 was repositioning,' said Harris, preparing this week for his final broadcast to the nation's insomniacs. 'Lovely word, repositioning. Basically it means I'm being repositioned from 16 hours a week to nothing.'

Harris's repositioning came as something of a shock for the million or so listeners who regularly tune in to his show. Sitting on the mixing desk in his studio, Harris has a heavy wodge of angry letters, several thousand thick. They come from across the country: from vicars in York, students in Lancaster and the night-shift at the Mr Kipling Bakeries in Petersfield, Hampshire. They talk of 'betrayal', 'horror', 'devastation' at the end of Harris's show. Many enclose copies of letters sent to Mr Bannister, most of which are vicious in their libel. All of them say their life will not be the same without Bob.

'It is something about broadcasting at night-time,' said Harris, lighting the first of his night's supply of Havanas to ripen up the whisper. 'It can inspire a tremendous loyalty.'

Harris started his show nearly four years ago. ('My last Whistle Test was on New Year's Eve 1979, and my first Radio 1 show was on New Year's Day 1990. So you can say the Eighties kind of passed me by.') He had just been repositioned by London's LBC and Johnny Beerling, then controller of Radio 1, thought his mellifluous delivery would be the perfect tone to take the station through the small hours.

While most disc jockeys simply seem to inhabit another world, Harris found that his new job took him into another universe altogether: that inhabited by computer buffs and long-distance lorry drivers, croupiers and hookers, cramming students and bored security guards. He played them an eclectic range of old and new rock, blues, soul, the kind of grown-up stuff that rarely if ever makes its way on to day-time Radio 1, delivered in the kind of soft purr that didn't jar at three in the morning. The listening figures astonished everyone, on the BBC's last audience satisfaction survey, Harris scored 7 per cent higher than any other Radio 1 DJ.

'I had no idea there were so many people out there,' said Harris. 'I just assumed I was talking into the ether. I think that because nobody advertised this show, people had to discover it for themselves, and therefore see it much more as their property.'

To prove his point, Harris said he would invite listeners to ring in on his dedication line; I could talk to them. The moment he gave out the number, the lights on the phones in his studio, each of which took up to 12 lines, lit up like Oxford Street in November. It was 2.30am.

'Hello, this is Sid,' said a voice through a storm of static. 'I'm just south of Scotch Corner on the A1 in me lorry, and I wanted to say the night won't be the same without Bob.'

'Hello,' said the woman on line 15. 'This is Carole from Andover, Bob knows who I am. Just tell him I've been in the pub, had a few drinks and now I'm tucked up in bed listening to him.'

'Hello,' said Dave from Essex. 'They call me the werewolf because I'm up all night and hairy. Tell Bob I'll miss him. He's the Bodleian Library of music. He knows so much.'

And so it went on; night-time is a lonely time and these people think of Bob as their friend. Now Bob's going they will have to retune their radios and form a new relationship. Matthew Bannister says he wants a younger audience than Bob's, which begs the question, how many 14-year-olds are up at three?

On the way home from Broadcasting House (Bob was still at work), I stopped at an all-night petrol station. At the cashier's window a man was buying 18 Bounties and 10 Bensons. From the open door of his car came the sound of a radio. It was the Bob Harris Show.

'Yeah,' the familiar voice whispered. 'This next one's for Brandon, who is just starting his milk round. Hi there, mate.'

(Photograph omitted)