It is strange seeing Judi Dench looking anything less than indomitable. It always seemed as though the soft, motherly, occasionally bustling exterior hid a core of steel.

But hampered by a bad knee that means she missed this year's Oscars ceremony, she looks temporarily enfeebled as friends rush to aid her up and down steps.

Dame Judi is nothing if not a trouper and that means ignoring the painful joint in order to fly to Berlin to promote the film for which she earned her Academy Award nomination as Best Actress.

She seems remarkably unperturbed by the fact that she is missing all the showbusiness razzmatazz in Los Angeles (not to mention the goody bags worth a year's salary).

Dame Judi already has one of course for playing Queen Elizabeth (Mk 1) in Shakespeare in Love. Eight minutes of icy hauteur won her both the Best Supporting award and the record for shortest ever Oscar-winning performance.

Though she is doubtless flattered by the plaudits that are heaped on her they are certainly not a motivating factor. She doesn't read her reviews and seldom sees the films that have the critics waxing lyrical about performances that can combine commanding presence with touching vulnerability.

It is partly to protect herself against her severest critic, herself.

"There are always 100 different ways of playing a scene, that is what is so irritating about seeing yourself on film. You think 'why on earth is that the one I chose, why is that the button I pressed at the time?'.

"My bathroom has seen the best performances I have ever given and it is all too late of course," she laughs.

She even treats the fact she has been made a Dame (in 1988) with a twinkle of amusement.

"It's a wonderful honour but it makes it very difficult when you go to America because a Dame is a different thing over there, though I quite like what it is actually.

"No one knows quite what to call you so I get 'Dame Dench' a lot. I think it's better to behave like a Dame but not necessarily add the bit to your name. It's just Judi.

"I don't think it has altered people's attitudes towards me, or at least I hope not."

In terms of national adoration she comes just below the Queen, according a to a poll conducted in 2002 to find Britain's best loved person (and Her Majesty probably only edged it because it was Golden Jubilee year).

Judi's is a stalwart presence, which is one of the reason's that the families of the British victims of 9/11 requested that she did the reading at the memorial service in Westminster Abbey.

On a lighter note, it was also probably one of the reasons that the makers of Casino Royale flew in the face of logic by keeping her on as M (the film was meant to mark the start of Bond's career yet when she was originally introduced in the role she accused him of being a dinosaur whose time was past).

There was more than a frisson of flirtation between her and Daniel Craig's Bond, possibly because they were more than equally matched as character actors.

Now 72, Dame Judi is in greater demand than ever but she has been a late bloomer career-wise – at least as far as films are concerned .

Born in Yorkshire, to a family of enthusiastic amateur actors (her older brother Jeffrey also turned professional), she made her performing debut playing a snail at the age of five.

Plans to be a set designer fell by the wayside after she decided she lacked the visual imagination and instead she applied to the Central School of Speech and Drama where she graduated with the prize for most outstanding student.

She joined the Royal Shakespeare Company in 1961 and became an accomplished stage actress (she holds a record six Laurence Olivier awards).

Her theatrical origins demonstrate themselves most clearly in the fact she admits she is very superstitious.

"I have a ritual that I start doing exactly the same thing at exactly the same time every night, I get a routine and stick to it rigorously, otherwise I feel that it is not quite right."

It was in a Stratford-upon-Avon pub that she started chatting to fellow RSC member Michael Williams, whom she married in 1971.

It was when she and Michael were united on screen in the tart yet tender comedy A Fine Romance, that they became household names.

Her status as the nation's (middle-aged) sweetheart was set in stone when she and her friend Geoffrey Palmer starred as old lovers reunited in the cosy comedy As Time Goes By.

Then, when she was in her 60s, she was reinvented as a film star after the intended-for-television film Mrs Brown was given a cinematic release and she was nominated for an Oscar.

In an impressive example of over-compensation she has racked up five more nominations in the last nine years.

Though she never gives less than her best, some of the characters have not really stretched her dramatically. Not so in the case of Barbara Covett, the treacherously lonely spinster that she plays in Notes On a Scandal.

When Barbara discovers the new art teacher she has become obsessed with is having an affair with a pupil she uses it as leverage to blackmail her into being her friend.

Cate Blanchett was also Oscar nominated for her work as the deeply misguided Sheba. However, Dame Judi is a revelation as Covett who is as pitiable as she is poisonous, lashing out at the object of her affection as she struggles to break free.

But she seems astonished that audiences didn't realise their national treasure – someone who in real life keeps cards in her bag so she never forgets a birthday and who adores practical jokes – had it in her to play someone so needy yet so calculating.

"There have been lots of parts I have played that are deeply unpleasant. I wouldn't say that Lady Macbeth is frightfully nice," she argues.

"We are none of us black or white, we are all shades of grey. I was just trying to find a person the audience would believe would act in that way and hopefully show why they are like that. Her behaviour is reprehensible but she doesn't simply come out of a reprehensible box, there is a journey."

It would seem difficult for her to empathise with someone so discontentedly alone as Barbara, although she says she did feel for the character when her cat – her only true friend – had to be put down.

"When my cat died I was completely inconsolable, as was my husband, as was our entire family, so I understood that

completely. But as actors we have to have another eye and huge ears because if we haven't actually experienced something, we have to have at least observed or have knowledge of it in order to make it real for people.

"Going back to Macbeth again, you don't actually have to have urged someone to commit a murder, there are ways you can find out how passion and ambition can affect someone and push them to an enormous extreme.

"You draw on what you have observed or read or know and then it's all about how you translate it."

Dame Judi and Michael were married for 30 years until he died of lung cancer in 2001. A few years after their daughter Tara Cressida Frances, known as Finty, was born in 1972, she brought her ageing in-laws and her mother to live with them. Family life was, by all accounts fiery, but never dull.

There was more emotional drama when three years before Michael died, Finty admitted she was two weeks away from giving birth. She had reportedly kept the pregnancy secret for fear of her staunchly Catholic father's reaction.

However, the grandparents-to-be soon rallied and Judi dotes on Sammy, who she says is the image of her late husband.

There have been other blows to deal with. In the 1990s the family lost everything in a house fire and Finty, who says she is as emotional as her father was in temperament, has been treated for depression and drinking since his death.

Dame Judi, however, is one of life's natural copers. After she was widowed she found herself possessed by a restless energy and threw herself into acting.

"I am working harder since Michael died," she has admitted. "You see we always made time for each other."

That time they would have spent together she now fills with film, stage and TV parts

She has just completed a successful run in Stratford in Merry Wives The Musical, and after she has recuperated from her leg operation there is the next Bond to look forward to as well as a role in the BBC series The Cranford Chronicles, adapted from the novels by Elizabeth Gaskell.

"Very often when you have played a part you get a lot of scripts which are very similar. If you are lucky enough to have a choice that is the last thing you want to do," she says.

She still enjoys the risk of performing, the plunge into the unknown.

With a career spanning half a century it would be easy to assume nothing could phase her but she admits that she doesn't read parts before accepting them "there is something in me that needs that fear.

"In the theatre you find parts that you think you know, that you know how to play it. I've always said that's the moment the man round the corner with the bucket of cold water comes and dashes it in your face and you suddenly realise that you don't know.

"Everything I have ever done has presented a challenge, I've never found it easy but that's why it is so exciting.

"What I look for is something completely different from what I have done previously. It is like Cinemascope, I am constantly trying to widen my vision.

"So next time I would like to do a film about a. . . circus performer. Something that's a challenge."