Helen Dillon in the garden in early summer

When she was little, just like her two brothers, Helen Rollo was given a patch to garden. Even at her hateful school, she was excused from the morning run around the games pitch and allowed to work in a spot in the greenhouse. Her childhood memories are of being told to wash her hands. "'No, those hands aren't clean enough, wash them again.' So now, I just don't care." There is, we agree, such a thing as good clean dirt.

(She is uninhibited about dirt: she reckons the dog, Mr Reginald - a loud little fellow with a tartan collar - has been rooting in something disgusting and gives him a couple of good sniffs. "I hate to think of where he had his face. It was very smelly and nasty whatever it was." She appears for interview in trousers and a jumper, and - apart from very nice jewellery - the outfit is undistinguished and practical for gardening. Her hands are black, and so far as I can make out at least two fingertips are covered with plasters. Later she apologises for looking so sloppy; I thought she looked just right.)

After a typical boarding-school education for girls of her class ("We didn't have to do anything except O-Level English, and we didn't even have to do that,"), she went to London to do 'debby' (my word, she agrees to it) sorts of things. She wanted to go to art college but her parents wouldn't allow that: she might have met "unsuitable people". She did a secretarial course, which she hated.

At 22, she went to the University of Surrey to study Russian but felt too old and left. She got a job for Amateur Gardening magazine and was taught to write by Anthony Huxley (one of the Huxleys). She did PR. Finally, she arrived on antiques - then an unsnobbish trade where effort was rewarded.

London in the Sixties was a good place to be: class seemed to fade as a measure of value. Yet, at weekends, she would often dip back into that familiar world, taking off to country house parties. If things had followed the socially ordained track, she "would have married a stockbroker and lived in Kent and done absolutely nothing," she says.

The Blue Border

"I did try and go out with stockbrokers from Kent, metaphorically speaking. I would get all dressed up in the right clothes - Sloane Ranger-type clothes. I knew the game; I knew the whole set-up. I would say: 'Right, I'll give it another try, to fall in love with the right man.' I used to go for weekends and I'd think: 'This life, I just can't take it. I don't see the point of it.'"

She kept hearing of the Irish antiques dealer, Val Dillon, on her buying expeditions up and down England. He'd either have just been or was just coming. He heard about her in the same way. Finally, they were introduced and a year later they married.

To her family, he was "quite way-out". "Not for the Irish bit, and not for the Catholic bit either, but for the fact that he was an antiques dealer. Nowadays it's very smart to say that your children work in Sothebys or Christies or doing antiques, but in those days it wasn't smart at all. I thought he was different. 'Thank God,' I thought, 'he's different. Thank God he's not a stockbroker from Kent.'"

They've been married for 28 years and she calls him, fondly, 'Grub'. They don't have children - something that hasn't troubled her. "I don't think I'd have made a good mother; I don't know why." For 26 years the Dillons have lived in Ranelagh, in a huge 1830 house, tucked off the main road. Its gardens are open to the public and are featured on The Garden Show (She is discreet about her former next-door neighbour, Mary Robinson [the first woman president of Ireland], but says enough to indicate that they weren't swapping geranium cuttings over the garden wall. The Dillons knew Nick Robinson a little better.)