They are the stuff of parental nightmares, the kind of incidents that - however hard one tries to dismiss them from one's mind - remain fixed there forever.

Most parents suffer them at some stage in their lives - it is an extremely fortunate father or mother who can't recall at least one incident in which their young child has had an agonising brush with death.

Kevin Whately is no exception. As he returns to our TV screens in The Children, an ITV1 three-part drama that revolves around the death of his character's stepdaughter, he is bringing back to mind the occasion when he thought one of his children was about to die.

'A bit of a lad': Kevin Whately stars as a philandering headteacher in ITV drama The Children

'I suppose the most shocking - because we actually saw it happening in front of us - occurred in Whitley Bay near Newcastle,' says Kevin.

'My son Kieran was about three at the time, and he just slipped from our grasp and headed off.

'He ran between two cars that were parked on the side of the road. There was fast-moving traffic both ways, and had he run another step he would certainly have been killed.

'To this day, we don't know what stopped him - we thought we were going to lose him, he seemed so oblivious to the traffic.

'Maybe he heard the screams from me and my wife, maybe he instinctively knew he had to stop.

'It was, unquestionably, one of the most terrifying experiences of my life. It's the kind you hope and pray no parent has to witness.'

Irreplaceable: Kevin in his best known role as Lewis alongside John Thaw, who played Inspector Morse

There is no such happy ending in The Children. Emily, the stepdaughter of Kevin's headteacher character, Cameron Miller, is found dead with a head injury in the garden of the family home, and much of Lucy Gannon's drama concerns who might have killed the little girl, and why.

The Children also deals with marital break-up and the way in which the offspring of broken marriages cope as a result.

Kevin's character is involved in disputes with his ex-wife Anne, played by Lesley Sharp - as well as sad and awkward attempts to build friendships with the stepdaughter of his screen partner Sue.

He has, the actor says, a 'roving eye' and is 'a bit of a lad.'

Indeed, we see Cameron cheating on his partner Sue with Polly, one of the teachers at his school.

Comedy: Kevin with the cast of Auf Weidersehen Pet

Kevin - better known for taking down people's particulars, in Morse and Lewis, than taking off his underwear for a sex scene - admits to mixed emotions when he read about his character's bedroom antics in the script.

He was flattered, he says, to be asked to film such scenes, at the ripe old age of 58, but hardly looked forward to shooting them.

'I think you will find few actors who actually look forward to filming scenes like that.

'And, in this case, I was working with actresses who had reason to be anxious.

'Geraldine Somerville, who plays Sue, had a tiny baby at the time and the very last thing she wanted to do was a sex scene.'

'And Anna (Madeley) was a screen virgin who obviously felt nervous about her first ever sex scene on TV.

'Rest assured I was very gentle with her, but it can't have been easy. However, you have to make such scenes look convincing.

'I may be shy - which makes filming a scene like this even more difficult - but Cameron has lots of self-confidence and is clearly a bit of a lad.'

Peak Practice: Kevin with Amanda Burton and Simon Sheppard

With one marriage ended and another relationship under threat from his philandering, Cameron's personal circumstances are in sharp contrast to those of the actor who plays him.

The former Morse star admits to being 'very fortunate', having been with actress wife Madelaine Newton for 29 years.

And if son Kieran - now a 23-year-old Bedfordshire-based builder - led a charmed existence when he was younger, then so too did his father's marriage.

It has survived a seismic shift in the careers of Kevin and Madelaine - when they first met she was the star, having played Dolly Seaton in the successful BBC drama When The Boat Comes In, alongside New Tricks actor James Bolam in the Seventies.

Their TV profiles started to change when Kevin found fame as Neville Hope in comedy drama series Auf Wiedersehen, Pet, in the Eighties, and shifted further when he starred as Sergeant Lewis in ITV's Morse.

The marriage also survived a reported affair in the Nineties, between Kevin and Amanda Burton, when they filmed the ITV medical drama Peak Practice together in Derbyshire.

Kevin has never discussed the allegation and neither has Amanda, who divorced director Sven Arnstein - her husband at the time - in 2004.

New kid on the block: Lewis and his new sidekick James Hathaway, played by Laurence Fox

Marital break-ups are common in modern Britain, so to what does Kevin owe the longevity of his relationship?

'I think part of it is down to the fact that neither Madelaine nor I is particularly ambitious,' he says.

'We even had an agreement, when we started having our children, that we would take it in turns to work but, because my career took off, that didn't happen.

'I console myself with the thought that she realised acting was a silly way to earn a living a long time ago and probably wouldn't have wanted to do a great deal more than she has done!

'We're on the same wavelength, we often instinctively know how each other feels about something.

'Of course, we are different in some ways - Madelaine is more romantic than me, I'm as romantic as a plastic chair. And we do row.

'I'd go as far as to say Madelaine and I love a good row, a vigorous difference of opinion - it helps clear the air!'

Madelaine has been a great support for Kevin, as he has dealt with the deteriorating health of his mother, Mary, 82, a victim of Alzheimer's disease.

'I'd be lying if I said it had been plain sailing. Mum is now very well looked after in a home, but the situation did put a heavy strain on Madelaine and my family before she went there.

'At one point Mum would decide: "Right I'm off home now", even though it might be 4 o'clock in the morning and she lived 300 miles away!'

These days, the caring Kevin and Madelaine love to look after their first grandchild, Ivy, who was born in December 2006 to their daughter Kitty, 25, and her partner Ben.

Kevin isn't known for emotional excess either on screen or off - but his face lights up when mention of his granddaughter is made.

'Ivy is a ray of sunshine who almost never cries,' he grins.

'She lights up our lives and we've been fortunate to see plenty of her since she was born.

'Her mum and dad are opera singers so when they were singing at Glyndebourne this summer, we would babysit for Ivy and have the time of our lives.

'Grandparents are meant to enjoy handing back their grandkids, but we actually fight to hang on to her, we love her so much!'

Kevin says he's a hands-on grand parent, just as adept at changing nappies as he is at running round the park.

'Ivy has made me feel younger, she's put me back in touch with my youth!'

Although Kevin loves sitting down and watching a DVD with Ivy, he won't be letting her anywhere near The Children.

Like much of what he films, it is strictly for grown-ups. And, with its marital bust-ups, unhappy children and blazing rows, it may prove particularly difficult for parents to watch.

'That may be the case,' says Kevin, 'but it's a gripping piece of television.

'The writer, Lucy Gannon, has the knack of writing about subjects that people are talking about, in this case the pain inflicted on children when parents break up.

'All three parts gripped me - although I accept it's increasingly difficult to hang on to a TV audience, in part because there are so many channels, in part because there's barely a subject these days, the soaps haven't covered already, whether it's incest, rape or murder.

'To find fresh and original drama is one of the biggest challenges facing television today.'

Kevin returns to the tried, tested and successful Lewis in the autumn, teaming up once more with Laurence Fox, husband of Billie Piper, who plays Lewis's sidekick DS James Hathaway.

It will be the third series of the detective drama.

According to Kevin, Laurence is about as far removed from his former Morse buddy John Thaw - who died from cancer in 2002 aged just 60 - as it's possible to get.

'Laurence is an Old Harrovian, John was a working-class lad from Manchester. But both, in different ways, have been a joy to work with.

'Laurence is outrageous, quickwitted with a wonderful sense of humour. He's fun to have around, he gets the whole crew laughing and he's very bright always aware of what is going on around him.'

And John? 'Well, he was a great friend and, as an actor, unique and, it seems, pretty much irreplaceable.

'His death has left television with a major problem - they simply haven't found anybody to take his place.'

• The Children starts on ITV1 at 9pm on Monday.