fifth wedding anniversary had been most enjoyable: a walk in the country with our five-week-old son, Max; spring lamb on the barbecue in the evening. When I retired upstairs, my wife, Marion, exhausted from breast-feeding, was asleep in bed, the baby in his cot alongside.

I was about to get undressed when my eye was caught by something unfamiliar, lying in the gap between the bed and my bedside table. Peering through the dim glow of a night light, I went to retrieve the object, idly thinking it might be a stray tie or a toy discarded by our two-year-old. As I bent down, I realised I was looking at a snake. Quite a large one. And not, so to speak, a normal resident of the house.

We live in Islington, north London, not in the tropics, and although many exotic things can happen around here, finding strange snakes in the bedroom is not normally among them. Furthermore, this creature, marked with a black and gold pattern, was nearly three feet long and an inch-and-a-half thick in the middle. As I approached, with growing incredulity, it began heading along the bottom of the skirting board, underneath the bed and my sleeping wife, heading towards the cot containing my son.

Placing myself between it and the cot, I peered under the bed; the snake raised its head and there was a glimpse of a forked tongue. I knew, because I'd kept one as a child, that it was not a grass snake, and it did not look like an adder. That left the poisonous snakes . . .

By now, my muttered 'I don't believe it' had stirred Marion. I tried to keep it relaxed, even jovial: '. . . er, darling, I . . . er, ha ha, hate to say this, but . . . er, don't panic, but there's a snake under the bed and I think you should take Max and . . .' Before I could finish, Marion had broken the world record for the five-yard dash from snake-infested bedroom and was on the stairs, shrieking her head off. I gave her Max and told her to go downstairs.

Grabbing a towel, I returned to the bedroom with the intention of using it to capture the beast. From somewhere in the recesses of my memory, I remembered I had to grab it just behind the head. But by this time, the snake had turned around and was heading back towards my side of the bed. To my horror, I realised it was disappearing into a gap between the floorboards and skirting board. I made a desperate grab but with a final contemptuous flick of its tail, it vanished into the hole.

What to do now? Downstairs, my wife was close to hysteria. So, despite the fact that I am a long-time crime correspondent and know this is not really their job, I called the police. 'Hello officer. We've got a snake loose in our bedroom. Can you help?' There was a pause, while they presumably tried to work out whether I was a nutter. 'Not one for us, sir. Perhaps you should try the RSPCA.'

The RSPCA were distinctly unfazed: 'Well, we would come round and take him away, if you knew where he was. He could be anywhere, couldn't he? Why don't you give us another call when you find him.' They were also unable to identify the creature: 'Probably isn't poisonous, but then you can't really take the chance, can you?' No traps or lures could be laid for it, apparently. We would just have to wait until it returned.

Deciding not to inflict ourselves on anyone in the middle of the night, we tried to sleep in the living room; my wife insisted on laying towels along the bottom of the doors. Just in case. By now, our two-year-old son, woken by the commotion, was enjoying camping out in the living room. Attempting to settle him, I grabbed the first video to hand. It was The Jungle Book: the one with the big snake that tries to strangle little boys. Marion immediately had another fit of hysterics.

The following morning, Marion and the children took refuge with neighbours. Back at the house, I ripped up a floorboard in the bedroom near the hole: no sign of the beast. But holes in the joists meant it could be anywhere.

Neighbours directed me to a house four doors down the terrace, where I was assured by Gary's mum that her son no longer kept snakes. London Zoo's reptile house said that, from my description, the snake was probably a harmless Californian king snake. But they could offer no possible means of catching it. Neither could the Enfield reptile centre: 'You'll probably be woken up one morning by it falling on your face.'

Several pest-control companies could not help, though one man said: 'It's a straight building job. We just rip up all your floorboards till we find it.'

By now, I was having nightmares: the creature could be anywhere. Marion would never sleep in the bedroom again and was nervous about the rest of the house. I had visions of having to sell the house on which we had just spent a good deal of money. 'Main bedroom: original marble fireplace, resident snake.'

Eventually, Gary was at the door: 'I fink you've got me python.' It had apparently escaped a month beforehand; almost certainly had worked its way along the terrace under the floorboards and been stirred into action by the warm weather. They get active at night, he said. Aren't pythons dangerous? 'Nah,' said Gary. He kept two: the big one, he assured me, would be too large to get through the woodwork. The escapee was smaller: 'If you annoy 'im, 'e might wrap himself around your wrist and hurt you. All you have to do is jab 'im wiv something sharp.'

What could I do to lure the beast into captivity? 'Not a lot. You could put out some water, 'e likes a drink. I don't mind what you do if you catch 'im. You can kill 'im if you like.' The zoo suggested trapping it by putting a water bowl inside a cardboard box.

That night, edgy and worn out, we settled down again in the living room, towels in place, water traps upstairs. At 2.30am I was woken and dispatched into the bedroom for nappies. Cazart] Just inside, there it was. I was not about to waste my second chance. I picked up the nearest weapon: a cat basket. Several hefty thwacks, and the beast lay curled and still. Using the cat's blanket, I picked it up and put it into the pillowcase I had ready. Taking my prize downstairs, shaking with an elation that was entirely primitive, I held it up in triumph for Marion, a hunter returning with a kill. She burst into tears.

I was not finished. I put the pillowcase inside a plastic rubbish bag and that inside a zipped canvas bag: I put the bag in the garden shed and locked the door. As I did so, the sense of relief was overwhelming.

The next day, I went to inspect my catch. There was a distinct wriggling inside the sack: the snake had simply been stunned. With a clear conscience, I delivered the beast to the RSPCA. That night, we reclaimed our bedroom. Bliss.

Two days later, Marion rang the RSPCA. The snake, it transpired, was thriving and was unlikely to have laid eggs under the floor. Unfortunately, the inspector told her it wasn't a python after all, it was a king snake. At time of writing, Gary has not responded to messages inviting him to identify his snake. My wife is convinced that somewhere in the woodwork another beast lurks . . .