So anyway, I think we'd been home for about half an hour on Wednesday night when Lisa realised she'd lost her engagement ring. It's a measure of the level of trust we have in our relationship that I spent the first thirty seconds assuming she was winding me up. I changed my mind when she burst into tears and barely stopped crying for the next four hours.

Having spent the evening standing on the hard shoulder of a motorway in the dark, wrestling with space blankets, trying to climb out of the cab of an AA lorry without breaking a leg, and fumbling around with gloves in a service station car park, there were naturally a few places she could have lost it. We spent an hour looking in all the obvious locations - bags, pockets, floor, car - and by midnight had moved on to the slightly less obvious places like the inside of a packet of cheese in the fridge. I'm not kidding.

I stopped the washing machine mid-cycle and emptied everything onto the kitchen floor, did the same with the rubbish bins, and Lisa even looked inside a Happy Engagement card from her mother which she'd opened ten minutes before realising she had no proof of engagement. Basically we checked everything that Lisa had touched. And that includes my cat. You could lose anything in her fur.

Shortly after midnight I phoned Pease Pottage services, which I have to say was probably the highlight of the entire search. The phone was answered by a woman who barely spoke English, so I carefully explained the situation to her and asked if anyone had found a diamond ring. She listened intently, then said something incomprehensible in another language. I said "I beg your pardon?", but by that time she'd already gone. Fortunately she passed the phone to someone whose level of English enabled her to string together a rudimentary sentence, so I explained the problem to this second lady, who listened in silence before responding with...

"What?"

For my third attempt I kept the story to words of one syllable, and having listened to my heartfelt plea for help, and sensed the desperation in my voice, the woman shouted "Phone back in morning!" and slammed the phone down. It wasn't quite the response I wanted, but let's face it, if your customer service skills were any good, you wouldn't be doing the night shift at a service station. This time last week she was probably clinging to the back of the Eurostar.

So at 1:15am, after further fruitless searching and a shot of caffeine to wake me up, I got in the car and drove all the way back up the A23 to Pease Pottage services to search the car park in the middle of the night. There was no diamond ring, but I did find a 5p piece, so it wasn't a wasted journey.

The search continued until 4am, then was postponed until first light, when I took everything out of my car in the middle of a snow storm. Thursday was spent co-ordinating the English-speaking employees of Pease Pottage, the AA, and the police forces of Horley, Crawley and Brighton, but all to no avail. We took Lisa's mother to Hove dog track on Thursday night where, in the middle of race 4, I received a phone call on my mobile from Tony, the AA man who'd rescued us from the M23. He'd turned his cab upside down but found nothing.

Friday was spent checking with our insurance companies, and discovering that neither of us were covered. You have to pay extra for a home contents policy which includes the loss of valuables, and until last week neither of us owned anything worth more than a fiver, so naturally we didn't have that level of cover. I wish I really had bought a cubic zirconia in stainless steel now. But still, if you've got a metal detector and you fancy a half-carat diamond in white gold, try the ditches down the M23.