It was on the fourth anniversary of my wife's death that I got to thinking about trying internet dating. We had lived together very happily for 10 years and married just before her untimely death. After the inevitable grieving process, my life was slowly starting to come into focus again. Dating after losing someone you love is strange: you feel unfaithful to their memory, but, at the same time, have been given an all-too-bitter lesson in life's shortness. So I dated a few women - we'd be introduced by friends - but none made me think about settling down again.

I did miss having someone special to share things with but, like many men in their late 40s, my opportunities to meet women were limited. My business - in the world of commercial trucks - could hardly have been more male-dominated. And I have never been a fan of going into smoky pubs and nightclubs to pick up the lady of my dreams. So I decided to give the computer a chance to find a woman for me: if it was as smart as it was always telling me it was, it should be a piece of cake.

I have never had any problem with women: thankfully, they like me. But I could not have guessed what I would be letting myself in for when I enrolled on a dating website; it was my introduction to a modern phenomenon, the older woman in search of sex.

After signing up, I looked at the profiles of the competition and concluded that most of them lacked humour. I decided that honesty would be the best policy. This is what I wrote: "Difficult, this bit, a little daunting, but here goes ... I did a poll among my friends and asked for no more than five words to describe me. This is what topped the voting: 1 Very funny. 2 A good friend. 3 Loves 'a bit of a do'. 4 Extremely good-looking (only kidding, I put that one in myself) 4b Terrible loser. 5 Too cheerful by half." I've got an ego as big as the next man, but even I was surprised to see that within 24 hours I had received 82 replies.

It quickly became clear that many of the profiles on these sites are total fabrications. Take education. All claimed a college education or a degree: don't women who went to secondary modern use dating sites? So I resorted to what we used to do at the youth club all those years ago: went for looks. That should have been the easy solution, but you try relating the 5ft 1in slender blonde to the dumpy, dark-haired figure waiting at the meeting point and looking impatiently at her watch.

I had been on the site only a couple of weeks before I met the first of what was to become a steady procession of correspondents whom I quickly named POWs - Predatory Older Women. She was waiting for me in the car park of the country pub, standing next to her car, enjoying the late autumn sunshine. She had the new version of the Beetle in a loud yellow. The vehicle, I soon came to understand, is your first clue to being in the company of a POW. (If she has a personalised number plate, you are normally in double trouble.)

Mary, as I will call her, appraised me carefully while saying hello. I was doing the same. She was immaculately dressed in a black Armani trouser suit - a seriously attractive woman. She had specified her age as 49 but swiftly admitted she was 52. Men, she explained, want younger women, so you get more replies if you are under 50. I know men are shallow - but please.

We had been in each other's company for a good 10 minutes when my next surprise came. We were sitting in a quiet corner of the pub, and I was sipping orange juice, when Mary told me in no uncertain terms that she was not looking for a serious relationship: what she wanted was uncomplicated sex three or four times a month. I must have looked shocked, because she raised a querying eyebrow. I recovered and asked if she was joking. Her reply still makes me smile. She said I looked like a man who would be "up for it". For a second, I thought I was being set up, and looked around for the inevitable mate with a camera. There was none.

Mary had children and grandchildren, was financially secure and enjoyed taking holidays with female friends. To my astonishment, we started a passionate affair within days. I had signed up to the website in the hope of starting a serious relationship and this wasn't really what I was looking for, but I am no idiot, and you don't look a gift horse in the mouth.

Fair play to your modern grandmothers - they know exactly what they want in bed, and are not afraid to demand it. If I had been a less stalwart man I would have felt intimidated. Thinking about it, I suppose it makes sense. Most single women over 50 will have had at least one long-term relationship. By that age, they've got rid of the kids, got rid of the man they don't want, and now it is time for them. Going to bed with them is often a double-edged sword: for the women I dated, sex was recreational. Their needs mattered to them more than mine. But the sex was almost always terrific, they take care of their bodies, are not afraid to tell you exactly what you should be doing at any given time, and you know that if they give you a compliment in bed, they mean it.

I was just getting to the nearly falling in love stage with Mary when she dumped me. That was another shock. The last time I had been dumped, I was wearing flares and had a 30-inch waist. Mary had class: she told me she was getting too fond of me (we were in bed at the time), so I had to go before I complicated her life. But it had been a great couple of months; we would meet for a drink, go to each other's houses. She was a lovely and formidable woman, very funny and excellent company. I would have been up for more commitment. I think it is more than likely that she had received a better offer, although I don't like to dwell on that.

Being dumped was the spur I needed to take the shutters from my eyes and enter the fray forearmed. I realised these women were not looking for a serious relationship, they were looking for fun. I decided that is how I would treat it. And if I met a special one along the way, so much the better.

So I licked my wounds, jumped in again and met "Kay", a sales director. She drove a Saab convertible with a personalised plate. Kay told me she was 48. I believed her until I saw the photos of her 50th birthday party on my first visit to her swanky home (terrific divorce lawyer: it was like Southfork in Dallas, only larger). She laughed at her gaffe, then distracted me by seducing me on the stairs. We did not even make it to the bedroom. That is another thing about the predatory women I met: they have developed exhibitionist tendencies late in life.

After Kay there was "Alice" and then there was "Sue" - all beautiful, good-looking women. And, to be honest, I have been amazed that these gorgeous creatures found me attractive enough to want to use me physically. They pay lip service to romance - but I seriously believe that these women are not looking for intimacy and commitment.

I am something of an expert on non-commitment, so feel able to judge. I was well into my 30s before I did commit to someone. Since then, dating has changed completely. Women are frequently taking the lead. Us older men have to adapt as well, so I now let a woman buy me a drink, and talk me into bed. As for the dating website, I haven't been on it for about a year. But I am ever optimistic, and still hoping to find the special person.

· Do you have a story to share? Email it to my.story@theguardian.com