THE Post Office taxi rank, opposite Bradwells Court, Cambridge, Friday 11.40 pm. Drinkers spill into the street. Some are simply good-natured, a bit rowdy. Others are running, screaming, swearing, threatening people with bottles.

I am sitting at the wheel of my taxi, breathless with fear. Only some of the pubs have chucked out so far; the clubs and late-night pubs are still to come.

I glance towards the long line of waiting cabs on the other side of the street. In this recession, Fridays and Saturdays are the only nights when drivers can make a fair living. All the drivers are out: mostly the unemployed, the middle-aged redundant and part-timers like myself. The rest of the time, I'm a writer. The 'pros' tend to work the day shifts, steering well clear of the yobbos who make Cambridge nightlife such a misery. Francis, Old Etonian, historian and, in better times, bon viveur, gives me the thumbs down: a signal that all's not well.

'Histon, mate,' the ruffian says as he slides into the back seat, 'and turn that effin' meter off.'

'I beg your pardon?'

'You mutton or somethin', mate? . . . I said, turn that effin' meter off]' He leans forward and smoothes the hair on the back of my head. A simple gesture, but one so full of menace that I crash the gears. I have just left the rank, but pull quickly back to the kerb and stop the engine. I look in the rear-view mirror. The ruffian is grinning. I turn towards him. He leans forward again, very close to my face. He belches. Sensing my fear, he continues grinning.

'Do you want a taxi or not, sir?' I ask, nervously. 'If you do, then the meter stays on.'

He is fair-haired, about 17. His face, flushed and coarsened from the night's drinking, blood oozing from one nostril, recedes into the darkness of the back seat. Despite the freezing cold, he is dressed only in jeans and a white, long-sleeved shirt. Food stains, mixed with his own blood, decorate the collar and cuffs. In his right hand he holds the remains of an empty lager bottle; the jagged end, perilously close to my neck, has already cut into the seat covers. He is undoubtedly a 'hard man'.

'Do you want a taxi or not, sir?' I repeat, sharply this time, refusing to be intimidated.

'Don't cop the strop with me, mate,' he says, as, raising one buttock from the seat, he breaks wind. 'Cop the strop with me an' I'll snap your effin' spine.'

His face looms into view again, so close I can smell the grease from the take-away food on his breath. Our eyes meet briefly. There is a silence. I remember the taxi driver, a pensioner, temporarily blinded in an attack some months previously. I remember gentle Peter, so traumatised by his own armed mugging that he has never driven a cab again. And 'Mouse', viciously and bloodily kicked in Cherry Hinton last summer.

I reach for my radio handset. 'Red alert . . . red alert]' No reply. I call again. 'Red alert . . . red alert]' Still no reply. The base operator is busy. There's no time to waste. I throw open the driver's door. I call out to Francis - now some five taxis behind me in the queue.

Within seconds Francis and four other drivers drag the ruffian from my cab. They prop him against the bus shelter as he mouthes obscenities; flailing at everything and anyone in sight.

'What's going on?' a student shouts from among a gathering crowd. 'What's going on?' he shouts again - and is karate-chopped to the ground by the ruffian.

I force my way through the onlookers. They are a mixed lot, late night revellers, a few dressed for dinner at one of the colleges. Veteran witnesses of small-town rural violence, they have long since learnt to look the other way. They fall silent as I lean over the prone student. I loosen his tie and call to Francis to get an ambulance.

While we wait, a pretty young girl scythes her way through the crowd. It is clear that she is not motivated by curiosity. She sits on the cold pavement beside the unconscious student. She takes hold of his hand. She presses his hand to her lips. She gathers her coat tightly around her body and sobs quietly into her sleeve.

The ambulance arrives. Word is that the student is concussed - nothing too serious. The ruffian has long since melted into the night with the police in pursuit. I return to my cab and rejoin the rank.

Before they are allowed behind the wheel of a cab, all taxi drivers must submit their pasts to scrutiny. A criminal record, in some instances even a flawed driving record, will possibly bar them from ever plying for hire. And yet, week after week, we hear of drivers being assaulted and, sometimes, murdered. Of course the public should be protected from the small rogue element which exists within the taxi trade, but what about the drivers themselves?

1.30am Four foreign English Language students cycle homewards after a night out at the disco. Two of them are girls. A local youth steps into their path. Swivelling on one grubby trainer, he turns his back on them, bends over, drops his trousers and gyrates his naked buttocks. 'Eff off you effin' froggies,' he yells, before stiff-arming one of the students to the ground.

'Disgraceful,' a well-dressed man says, half to himself, as he passes my cab, 'damned disgraceful. Tch, tch. You expect this sort of thing in London . . . but Cambridge]' He could be a politician, I think, for no good reason. I feel I should run after him, shake him and scream: 'Look, mate, it's everywhere. Can't you see? The violence is everywhere . . . what are you going to do about it?' I know what at least one Cambridge college - Churchill - has been forced to do about it: make taxis freely available to any of its undergraduates who find themselves in the town alone late at night.

2.20am I pull on to the rank behind four other taxis. As I do so, a glazier passes me in his van; off, no doubt, to board up another wrecked shop window. A police car, streaks through Market Street.

The food stall is doing a roaring trade. Groups of young men, most too drunk to care, wander about coatless in the cold, early morning air. A couple of beggars home in on one group. They are despatched in a hail of empty Coke tins and half-eaten kebabs. A solitary figure urinates through the railings of Great Saint Mary's church.

I am worried about Francis. I haven't seen him for a couple of hours. I enquire on the CB. I am told that he went off the road an hour earlier. A passenger vomited in the back of his cab.

5.10am After 12 hours during which my sensibilities have been not so much offended as laid bare, I'm home. My wife and daughter are safely asleep upstairs. At least, I hope they are. I tiptoe upstairs to make sure. Reassured, I tiptoe back down.

There is a note on the kitchen table: 'Potato pie in the fridge. Help yourself. Pud in cupboard. Love you, darling.' Lots of kisses, and then a PS: 'Steve phoned. Will you drive his taxi tomorrow night?'

My appetite, for some reason, deserts me.

(Photograph omitted)