Diary of a tireless busybody Jenny Agutter, one of Britain's most consistently successful and thoughtful stars, reveals what it was like to play Alan Clark's wife in the eponymous Diaries series

At Saltwood, in Kent, this was just one of several bizarre and fleeting encounters between the widow of a consummate philanderer and the actor chosen to climb inside her skin. ''Somewhere I have a photograph of that moment with both of us in our identical outfits.'' Jenny Agutter chuckles at the weirdness of the memory, the sensation of

looking into a mirror, knowing the likeness reflected there is not you, but a stranger.

Yet Agutter's physical resemblance to Jane Clark, the long-suffering wife of Alan, that late high Tory cad, seems uncanny, and required only minimum make-up for the serialisation of Clark's uproariously improper diaries now running on BBC4. ''I don't think we are all that alike in looks, but I'm not too far off her taste in clothes - crew necks and comfy old cardigans, some with holes in them. But Jane has lots of scarves and Barbours, which aren't really my style. I'm more a jeans person and I am afraid I've got holes in them, too.''

Like most who meet Jane Clark, Agutter was struck by her resolute girlishness which can't quite disguise an enigmatic personality. So, how difficult was it for one of Britain's consistently successful and thoughtful stars to portray a living character who remains elusive?

''Well, the series is really composed of vignettes and my job was one of regarding someone rather than delving. I wasn't asked to analyse what was going on inside Jane Clark's head at the time when his infidelities became known. And to be honest, I don't think anyone can.''

What Agutter tried to capture was Jane's coping strategy, a combination of straightforward strength and buoyant charm. ''Mind you, that sort of easy affability can cover a hell of a lot and I felt she used it as a

barrier against personal intrusion.''

And, says Agutter, Jane is ever on the move, a whirl of activity which is the reliable tactic of distraction employed by someone with no desire to be pinned down. ''But I didn't necessarily feel she was masking a great weight of unhappiness. On one occasion, I asked her why Alan nearly always referred to her as 'little Janey'. She is tiny, much smaller than I am, but I wondered if she felt the description was patronising. Or was it because they married in 1958 when she was only 16? But the reason, she said, was simple. It was merely to

differentiate between her and her mother-in-law, also called Jane.''

That in itself might strike some as Freudian. He was 30 when he

married, and as the years passed into wedding anniversary decades - four in all - Clark's child bride became, in effect, his mother figure, the person he continually hurt but whose advice he always sought, and the woman to whom he returned no matter the intensity or blackguard mischief of his betrayals.

In the course of conversation with Agutter at her home in south-east London, I mention time spent with the Clarks during the 1977

general election campaign, when they were out on the stump in Kensington and Chelsea, the seat Alan Clark represented until his death from a brain tumour two years later. Clark had resigned from his Plymouth Sutton constituency in 1992, but for him the easy life of retirement proved ''a colossal mistake'' and on that sunny day of canvassing in wisteria-draped Chelsea, Jane Clark confided with genteel forbearance that: ''Once Al realised he'd cut himself off from the Commons, he missed it all terribly. For him, that lost life was awfully distressing but it didn't bother me at all.''

Was that an example of upper-crust English phlegm, whereby a spouse never jeopardises personal status by becoming too flustered about one's partner's passions? Agutter thinks it's more akin to army training than upper-class etiquette, the army being something she understands as the daughter of a British officer. Her childhood involved many postings abroad and, in fact, Agutter exudes that sense of duty and brisk efficiency which identifies officer material. a tireless campaigner for a string of charities, she is, in truth, a bit of a busybody. ''I'm not political but I can't not complain if I see something wrong.'' So, among her harangues are late trains and dirty transport, street

litter, lorries in bus lanes, supermarket queues and homelessness.

''I think a certain insularity happens to people in the army which makes them very self-sufficient and, in a funny way, that sits well with the Clarks. They didn't really belong to an upper-crust hunting, shooting and fishing society. He, in fact, was very much against all that and it is not what Jane is about at all.''

In fact, Jane, territorial in domesticity, recently told the journalist Lynn Barber that she didn't really have time for friends or feel the need for them. Her life, it seemed, revolved around gardening, cooking and patching up things in Saltwood, the part-medieval and part-nineteenth-century castle.

''She is extraordinarily fit and never stops moving. But Jane wouldnot be the person she is now if all along she hadn't had huge strength of character.'' Certainly that quality is something both women share. Agutter, at 51, still possesses an ageless gamine grace which disguises steely independence. She has always looked younger than her years, but her film career actually began 40 years ago when, aged 12, she was signed up to play in East of Sudan.

''I probably looked about eight then and I think I got the part because I was light in weight and the role required me to be carried around by Sylvia Sims and Anthony Quayle. In fact, my audition consisted of walking into a room and being bodily picked up by the producer and the director who just said: 'OK, you'll do.''' From then on, and without any drama school credentials, Agutter has rarely been out of work. And there are two films in this long career which have guaranteed her movie immortality: The Railway Children, directed by Lionel Jeffries from the Edith Nesbit novel, in which she played the sensitive, responsible eldest child, Bobbie, and Nick Roeg's mesmeric Walkabout in which Agutter, perceived by audiences as an untouchable English rose, swam naked in a scene symbolising the rite of passage from innocence to womanhood.

''It was like a garden of Eden sequence and after that moment the film changed into something very bleak. I was 16 but Nick talked a great deal about the importance of that scene and, because I respected his integrity, I was convinced the nudity was the correct thing to do.'' Even so, Agutter was far more self-conscious than extrovert about the proposal and once the scene was over, she hurriedly emerged from the water shielded by towels, only to discover that the film crew were entirely stripping off to enter the water in an act of solidarity. ''The continuity girl, a wonderful character, went even further to make me feel less embarrassed and wandered about topless the whole time.''

What isn't so well known about Agutter is that she spent close on 20 years in Los Angeles as a well-adjusted singleton unimpressed by the gaudy vanity of the town's inhabitants. Indeed, Agutter didn't marry until she was 37. She had met Johan Tham while filming in Bath with Richard Harris and Ben Kingsley but Tham, a wealthy Swedish entrepreneur, was nothing to do with the film industry. He owns a select chain of hotels which once included Cliveden, the palatial

former home of the Astor family.

''I suppose I'd been unattached for so long that I was quite prepared to carry on that way and, anyway, in LA I'd rather given up the idea of finding the right person. Sadly,

relationships are really not the best there because it's a fact that the men in this business are not the most mature. Movies make for a Peter Pan world.''

It is interesting that Agutter uses that particular reference because Jane Clark, in as much as she talks about her husband's rakish behaviour, puts it down to his Peter Pan-mentality, a terror of growing old. Although Agutter cherishes her metropolitan family life with Johan and Jonathan, their 13-year-old son, she can understand Jane's pleasure in solitariness. ''Before I met my husband I'd reached that single state where I felt settled in myself. One of the advantages of being on your own is that there is nobody close to see your bad moods. You don't snap at anybody because there's just you.''

But marriage has taught Agutter that vulnerability as well as strength can be shared. ''If you are in a

trusted relationship where you know the other person wants you, then you also know they'll take the good with the bad.'' Jenny Agutter waited a long time to be convinced of that blessing but today it is one of the most shining reasons for what she calls her charmed life.

The Alan Clark Diaries, BBC4,

Thursdays.

CV

Born: December 1952 in Taunton, Somerset.

Education: Spent mostly abroad when her father, a British army officer, was on overseas postings.

Career: Child star from the age of 12. Credits include Ballerina, The Railway Children, The Man In The Iron Mask, Walkabout, The Eagle Has Landed. Also Shakespearean roles in King Lear, Love's Labour Lost and Romeo and Juliet. Has concentrated on television drama since the 1990s.

Marriage: Husband, Johan Tham, a Swedish entrepreneur. The couple have one son, Jonathan, and live in London and have a cottage in Cornwall.

Interests: Much charity work to raise funds for cystic fibrosis, ovarian cancer research and the National Coalition for the

Homeless.

Highs: ''The birth of our son. At 38 I was completely overwhelmed

by it.''

Lows: ''Driving through the night once and for absolutely no reason, I began thinking about my parents' vulnerability now that they are getting old. I became just terribly upset at the thought of anything happening to them.''

Born: December 1952 in Taunton, Somerset.

Education: Spent mostly abroad when her father, a British army officer, was on overseas postings.

Career: Child star from the age of 12. Credits include Ballerina, The Railway Children, The Man In The Iron Mask, Walkabout, The Eagle Has Landed. Also Shakespearean roles in King Lear, Love's Labour Lost and Romeo and Juliet. Has concentrated on television drama since the 1990s.

Marriage: Husband, Johan Tham, a Swedish entrepreneur. The couple have one son, Jonathan, and live in London and have a cottage in Cornwall.

Interests: Much charity work to raise funds for cystic fibrosis, ovarian cancer research and the National Coalition for the

Homeless.

Highs: ''The birth of our son. At 38 I was completely overwhelmed

by it.''

Lows: ''Driving through the night once and for absolutely no reason, I began thinking about my parents' vulnerability now that they are getting old. I became just terribly upset at the thought of anything happening to them.''