I have been in love continuously since I was 15. I must love to be in love. Or, maybe it is still a novelty. I was born and raised in Kampala, Uganda. For us, Asian Shia Muslims, marriages were smart deals between families based on economic advantage and genetic improvement. Marrying up was a good move a dark boy getting a fair girl even better. My generation inspired by pop songs and Hollywood was the first to reject arranged marriages and go for Romance, big time.

My first love was a boy with curly hair and a cute smile, a Hindu, therefore forbidden to a Shia Muslim and so dizzyingly exciting. I was 15. There were kisses, wet, clasped hands in the cinema, early Beatles songs, secret love poems passed in class (for which transgression he was brutally caned by the Head). No sex I was good girl, I was. So he found another who was happy to go all the way, a spoilt, rich miss. Love hurt for the first time.

Then, when I was 17, number two turned up, in the back seat of a car, on the way to a rock'n'roll party. He was so handsome. I was not at all pretty but funny and clever. We danced, clicked, later committed, went to university together, moved to England, married in 1972, got into Oxford for postgraduate studies, had a son, moved to London, deeply in love, forever and ever. We were ardent and true. Then came prickly times, signs of change. I was becoming politically engaged, and less girly. He was laid-back, loved Clapton and Santana (and by now looked like the latter).

When I turned 39, he was off, with a young blonde. The hurt and loss were volcanic. I was grievously burnt. "No more men" was the promise I made to myself, bitter and alone. Four months later I met this gorgeous Englishman in a taxi queue at Bristol Temple Meads station and fell into his blue eyes, in love again, almost instantly. Nothing would come of it I thought. He was clearly gay as he wore an earring and said he lived in Islington. Six months later he had moved in with us. My son, only 10, was devastated when his dad departed and still hoped for his return. But the sweet Englishman won him over, making the child promises he has never broken.

My forties were up and down, full of flooding emotions. One love had fled and turned cruel, and a new love had broken into my grief and made me believe and tingle again. We got married, partied all night at the hotel in Paddington where we had had a drink after coming back from Bristol. Then, in my mid-forties, came another child. I was ecstatic and fearful. Children make you victims of the fathers. What if he dumped me too?

Now she is 15 and we are in our fifties, still truly, deeply in love though not madly, not as we were in our first decade together, when everything that was happening to us seemed improbable. Then we were reckless and wild, dodging the fallout from an acrimonious divorce, crazy about each other, high.

We still passionately want each other, in bed, in life. Without lust, without sensuality, without spirited conversations, this relationship would have turned dull, comforting and repetitive. His intellect and artistic sensibility excite me even when I don't agree with his views and opinions. I spent over 20 years with a man who was more keen on himself and wildlife than politics and society. I too like tigers and rhinos but they don't set me alight.

In the first years of this marriage, we were still too polite, careful not to push things because what we were building was fragile and precious. Now we let sparks fly when we argue or debate issues. In this marriage there is a coming together of the head, body and heart. He is so different from me male, analytical, rational, Western, supremely elegant in argument. I am emotional, verbally dextrous, witchy. The West and East clash and yet are irresistibly drawn to each other. Oh yes, I like to pretend cosmic and global forces are present in the marriage.

Our daughter thinks our home is too argumentative, too noisy. Perhaps she is right. We should try to calm things down a little, not get quite so animated over, say, George Bush, or Iraq (subjects on which we agree) or alternative medicine and ghosts (on which we will never agree). Sometimes these rows make our wine glasses shake and tinkle. But yet, a hushed home, with nods, small talk and ritual, would evoke for me the silence of a grave.

Food is the other great joy in this marriage. I am a good cook and he eats and drinks heartily, my very own Grard Depardieu. Sure, we have put on flesh here and there, but in our fifties, it doesn't matter much. That anxiety over the imperfect body has gone and brought an ease I have not experienced before. We want each other, as we are, an unexpected gift.

I asked my husband when writing this: "How do you feel about love at our age?" "Lucky, lucky to have such love." Yes, that's the one overwhelming feeling. I pray for safety and continuity, for it to last. What will he or I do without the other? Mortality lurks and friends are snatched away; others flee their marriages or have been around each other too long, seem to be in a slow decline. Fear deepens. I see shadows of death, divorce, decay and illness and picture the worst that can happen, as if putting myself through imagined anguish will keep such tragedies at bay. One day, too soon, it will be over. The intense flames of our late love will be no more. But we knew it once. Few at our age are that blessed.