LAST week, out of the blue, I got a telephone call from an old friend.

"It's Karen," she said. "Who, Sharon?" I replied. "No, Karen."

I racked my brains" Karen, remember? We shared a flat for four years."

"Oh, God, KAREN." I yelped, "How did you find me, what are you doing, where are you living?"

It's hard to know exactly what to say to someone who was, for five years, your best mate, but who you haven't heard from for more than a decade.

It's the same with any old friend. Having them call you is great, but at the same time disconcerting. You're stuck in the hum-drum life you thought you'd never have (and still can't believe you've got), Mrs Average with a husband, a mortgage, 2.2 children and all the mundane domesticity that goes with that.

And you immediately imagine the sort of life your friend-from-the-past is leading: great bloke, great house, great job, great social life.

And, as you glance down at your figure -- unrecognisable from the good old days -- you imagine she's still the same size and shape, slim, trim and trendy. You want to hear about it, but at the same time you don't.

To my surprise, it turned out to be quite the opposite. My friend did have a high-flying job and a nice London flat, but had given up both to re-train and was now living a simple life on the south coast working to stop seaside erosion. She sounded just like the old Karen I knew as a student, when we shared a flat that made the bedsits in Rising Damp look like the Paris Ritz.

While she wasn't embroiled in bringing up young children, she confessed to having put on weight and to feeling the sort of disillusionment felt by me, and many other women in our mid-life age group. Most amazingly, she sounded quite taken with the boring details my own life.

I'm rambling on about all this because I've just heard about the launch of Definitely Day -- a special day designated to encourage people to make sure they get in touch with old mates.

It follows a study of 500 people which found that once Brits hit the age of 35, they tend to lose touch with friends because of work and family commitments.

Though it's not always a case of losing touch. Sometimes, circumstances drive you apart. I did maintain contact with one very good friend, but my children came between us. She refused to acknowledge that as a mother-of-two I couldn't go out and behave like the giggly juvenile delinquent she knew and loved.

With my children in tow, all that ringing doorbells and running away, all that stuffing tennis balls up car exhaust pipes and nicking traffic cones to furnish my bedroom had to end. I had to be a tad more responsible - but she couldn,t accept that, so we fell out. And there are some old acquaintances you would rather forget. Women in particular hate surprise visits from their husbands' former friends. I can think of a couple of vile creatures who I really would not be thrilled to find on the doorstep.

Pals from the days when my husband was a boozy, laddish type who stayed out late and didn't call, they would almost certainly expect the same of him today -- and no doubt he would be only too happy to oblige.

While we were on the phone, Karen did tell me about another friend from our student days who now works in the fashion industry in New York.

"He has this incredible loft apartment with long windows overlooking Manhattan. I'll give you his address so you can get in touch." I'm not sure I dare, even if it is Definitely Day.