It was almost 9pm and the sun was setting as Martin Kelly, a gifted plastic surgeon, arrived home in Fulham, southwest London on May 20. It had been a long day: the 43-year-old specialist in facial reconstruction had spent hours in the operating theatre, attended an early-evening meeting, then dashed back to the Chelsea and Westminster hospital to check on a patient.

Kelly had already telephoned a friend who was joining him for supper to say he was running late: as soon as he got home he dropped his briefcase in the living room and walked onto the balcony to phone his wife, the actress Natascha McElhone, who was in Los Angeles filming the second series of Californication. He got her voicemail.

Four days earlier it had been the couple’s 10th wedding anniversary but they had decided to delay their celebrations until the following week, when Kelly would be flying out to America. They planned to spend a night at the historic San Ysidro ranch, in California, then go for the 20-week scan on the baby McElhone was carrying, a brother or sister for their sons Theo, 8, and Otis, 5.

“He left me this message, full of the joys . . . he couldn’t wait to come out the next week, he was so excited about the scan, so excited about the baby,” she says. “Thank God, a lovely last message.”

Little more than 10 minutes later - McElhone calculates it as 13 - Kelly was dead. The tall, handsome doctor, who played in a band and had been snowboarding five weeks beforehand, was found by his friend lying in the hallway, one foot wedging open the front door. His heart had suddenly and inexplicably given out.

There was a lock on Kelly’s mobile phone, which meant nobody could access McElhone’s or any of his family’s numbers. For the next few hours she kept filming 5,000 miles away, unaware of the drama back home, where her husband’s body had been taken to the Chelsea and Westminster hospital after frantic attempts to revive him.

The couple’s sons were with McElhone in California and she had booked them into afternoon gym classes just across the road from the studio. There was a break in filming, so she had walked over to watch them when she picked up a message from her husband’s best friend, Neil Randhawa, a consultant anaesthetist.

“He said, ‘It’s really important you call me.’ I wasn’t at all worried about Martin because I’d had this lovely message from him. I thought there must be something wrong with Neil, so I rang just to check he was all right.

“When I got through, he said, ‘Are you alone?’ I guess Neil didn’t know how to tell me. He kept saying everyone did everything they could and I remember thinking, ‘What on earth is he talking about?’ It was the most surreal moment of my life. It occurred to me that maybe he was asleep - it was one in the morning in London - and he was rambling.

“I walked across the road towards my trailer and it must have suddenly hit me on some level. I did that thing I thought people only did in movies - I dropped the phone and my knees sort of buckled under me. A lovely woman called Nancy, who is David Duchovny’s assistant, ran up to me. I told her the boys were over in the gym and asked her to fetch them. I got into my trailer and called Neil again. I knew I was going to have to tell the kids. I thought of trying to suspend time or wait and not tell them for a day but I couldn’t bear the idea of other people knowing and them not. I remember looking out of the window and seeing them chasing after each other with huge squeals of delight and thinking, ‘I’m about to shatter their world.’ They came in and they were like little boys are, full of energy and excitement, and I told them what had happened. And then the clouds descended . . . it was awful.”

Fast-forward almost four months and we are sitting in Bibendum, Terence Conran’s stylish restaurant in South Kensington. McElhone, 36, is wearing a red velvet scarf her mother wore when she was pregnant with her: “It’s stayed the course well, don’t you think?”

She is even more beautiful than the publicity pictures suggest, with her sculpted cheekbones and eyes of clear, dark blue. There is nothing to suggest the grieving widow, except a fleeting closure of her eyes and a silence after she describes telling her sons they had lost their father.

If the mark of a fine actress is an almost superhuman control over her emotions, McElhone must be up there with the best of them. Her serene smile hides what must be the most dreadful turmoil. In the days after Kelly died, she wrote a heartrending tribute: “I just can’t believe I won’t feel his skin any more, how is that possible?” Now, she professes to be “moving on” - working diligently through the legalities, because Kelly had not made a will, and preparing for the new baby, due in four weeks - though she admits to still feeling dazed. “It’s the closest I’ve ever felt to being hit by an avalanche.”

She attributes her sense of calm and practicality to the children. “I haven’t been able to go off into a corner and be self-indulgent,” she says. “All the decisions have been made for me in that respect. There’s no ‘Shall I crumble or shall I rise, phoenix-like, from all this and take on the world?’ - clearly, I can only do the latter. My boys are like little Duracell batteries that slot in in the morning and I’m charged up for the day. I’m lucky.”

Still, she has surprised even herself by how optimistic she feels about the future. “Martin is really, really present, which I’m surprised by and delighted by. I’ve never been one to believe in spirits, but I feel we’re all suffused with him in different ways and that will live on, in me, in the kids, in this new little one that’s just coming along. The amazing thing is how you can keep going if you have to. You can see that by looking at people in far worse situations, in disasters or war-torn countries . . . and that is how you feel, a bit like a refugee, as if everything that belongs to you has been broken.”

Before he died, Kelly had been working with fellow surgeons on developing a gel to treat postoperative scarring, appropriately called Heal. In testing it on patients, they found that it not only reduced scarring but could be used to treat everyday injuries such as sprains, sunburn and bruises. They believed it deserved a place in every bathroom cabinet. McElhone, who was helping with testing, used it on her son’s sunburn and says the redness disappeared within hours.

Heal gel is available online, and if it seems incongruous that, having so recently lost her husband, she is out promoting his product, McElhone doesn’t see it that way. “A lot of people said to me, ‘For God’s sake, Natascha, be realistic - you don’t know what’s happening financially, you don’t know when your next job is, you’ve got a baby coming and the boys and your own grieving and you can’t take on what he’s left behind.’ But to me it’s all I can do: Heal is his poem, his legacy, part of his contribution to the world, and if I don’t do what I can, I’ll be failing him.”

The couple had known each other for 20 years. When McElhone was 16 and studying for her A-levels in north London, she had a weekend job as a greeter in a restaurant. One of the barmen was a student who lived in Camden, near her school, and told her she should drop round. Kelly was one of his flatmates.

“This Adonis opened the door and I was slightly gobsmacked,” she says. “He was very casual but he claimed, many years later, that his heart skipped a beat too when he saw me. I can’t quite believe that. He was about 21, and that’s such a big difference at that age. He was a medical student and he’d already achieved so much.”

Born to a French father and Irish mother, Martin Hirigoyen (he later adopted his mother’s maiden name because patients found his name so tricky) was educated in Paris and at Winchester college. By the time he and McElhone got together, in 1996, he was a senior house officer and she had just made her first major film, Surviving Picasso, with Anthony Hopkins. She went on to star in The Truman Show, with Jim Carrey, and Solaris, with George Clooney.

Soon afterwards the international medical charity Médecins Sans Frontières was looking for a volunteer team of surgeons to do facial surgery in Taliban-controlled Afghanistan, and Kelly flew to Kabul. “It was a pretty dangerous place and I remember being really worried about him and thinking, ‘Why am I so worried? I must really love him’,” says McElhone.

One of the children Kelly came across was four-year-old Hadisa Husain, whose skull had not fused in the womb, leaving part of her brain exposed. She had no nose and her left eye was obscured by folds of flesh. Kelly discovered that she was known as “devil child” and had been stoned by villagers. Conditions were not sophisticated enough to operate on her in Kabul, so he raised funds for her to be flown to Britain.

A little while later McElhone was filming in Cambodia with Gérard Depardieu and Matt Dillon when she came across Beat Richner, a Swiss paediatrician and cellist, who had founded four children’s hospitals. “Martin visited and saw craniofacial deformities that never got treated, families who were ostracised, and he determined to do something,” says McElhone. “We’d always had this thing of, ‘Oh, when we’re old and grey we’ll go and live in the Third World’ and I would try and teach English or do something useful and he could train local surgeons. And he said, ‘Well, why wait? Let’s try and find a way of doing some of this now.’ ” The result was Facing the World, a charity founded with a group of leading craniofacial surgeons, which has treated children with disfigurements from around the globe. Meanwhile, Kelly was steadily climbing the career ladder, appointed consultant to both the Chelsea and Westminster and the Royal Marsden hospital, where he reconstructed faces after cancer surgery. His private work made him a favourite among London’s glitterati - he is reputed to have repaired Tara Palmer-Tomkinson’s nose after it collapsed through cocaine use.

No wonder McElhone’s tribute painted him as a Renaissance man. He continued to play with fellow surgeons in a band called Tuck That and was a keen sportsman. “He taught [the boys] chess, surfing, drawing, foreign languages, his version of truth, what it is to risk, to have integrity, manners - beautiful, manly manners - and how to leap into the unknown at least once a day, because not knowing what you might find was the real gift of life,” according to McElhone. Her greatest sadness was how much their sons would lose out on. “Their world for now has been halved: I cannot become him,” she said.

At first she found it difficult even to speak about Kelly. “I was talking to Elizabeth Waterhouse, who is married to Norman, Martin’s mentor, and said I felt that every time I shared thoughts and memories, every time I opened the bottle of him, as it were, I lost a little bit of the scent. I wanted to keep it corked and sealed so it retained its potency.

“She said, ‘I don’t know why you’re afraid of losing any of the memories or losing him in your life.’ She said she remembered the first time she’d met me. Martin and I were quite young and we were goofing around in the garden, climbing on top of each other, not realising anyone was watching. She said, ‘I was struck at your wedding that he’d adopted so much of what was you and you’d adopted so much of what was him.’ So as well as having children who’d fused us, it was comforting to think that some of what was him had rubbed off on me, so it’s in me as well as in the boys.

“We went to see Martin’s father last weekend. His great-grandfather was an engineer during the industrial revolution and Theo was just sitting listening to stories about him, spellbound. So it’s lovely that even though his dad’s gone, there’s this legacy. He likes the idea of being a nuclear physicist and he can think, ‘That’s okay, I can be interested in science because all the men in my family are interested too.’ ” She has made memory boxes for the children. “I only started doing two, and I suddenly thought: poor little lamb!” she says, patting her stomach. “I was lucky - they had exactly the same leather-bound box left in the shop.” Kelly’s best friends have recorded CDs of his favourite music and written letters to the children so they will get an idea of what their father was like.

After his funeral McElhone held a wake. She could not trust herself to speak, so she put together a film of Kelly’s life and times. “We’ve got a little projector and a screen and six people at a time went upstairs and watched it on a loop. It was supposed to make everyone laugh but of course they all came down in floods of tears,” she says.

There is a copy of the film in each of the children’s boxes, along with pictures they drew and notes recording their thoughts and impressions after their father’s death. McElhone is there if they want to talk about him, but they don’t dwell on it. “I had this irrational fear at first that by moving on I would be leaving him behind. But that’s obviously what you must do, as a parent. I have grabbed life by the throat and I am packing in as much as I can and trying to keep things fun for the boys, actually. They seem to be responding in a very positive way. From what I can tell, and it is so hard with kids to know, I don’t think they feel that a door’s closed. I think they still feel there are many doors to be opened and I want to keep that alive.”

She thinks Kelly would approve. “On our last weekend together we took the boys up to the sequoia forest in California. Funnily enough, we spent much of that weekend discussing Heal and how I could help . . . Martin, as always, was full of verve and energy, looking to the future. We climbed high up, onto these huge logs. And that’s my lasting image of him, sitting, swinging his legs, smiling down at me.”

For more information on Heal visit: www.healgel.com

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