GREY-HAIRED men pushing infants in upmarket buggies can be identified as fathers rather than grandfathers by the permanent smile and the unconscious straightening of the shoulders. They have suddenly become a noticeable phenomenon; a 21st-century consequence of twentieth-century social change which has progressed to where "broken families" are gradually being replaced by "new families".

In human terms, it means simply that happiness can follow heartbreak. Five years ago, many Herald readers were moved by Derek Bateman's account of the death of his wife, Alison, from cancer. Then a presenter of Good Morning Scotland on BBC Radio Scotland, Bateman argued that, as a society, we were all - relatives, medical staff, religious leaders and legislators - failing to face up to the painful reality of death. "If anything good can be taken from our experience, it is the knowledge that personal tragedy can be confronted and that, while the old anxieties remain, death is not always to be feared, " he wrote. It was a heartfelt account and did not make easy reading.

So when a colleague on BBC Radio mentioned on air yesterday that Bateman would be absent from his weekend show because his new wife had just had a baby, it was a heart-lifting moment for many. Indeed, a quiet joy is audible in Bateman's voice as he explains: "Alison died in 2001, and remarkably shortly after that, Judith Mackay, the editor of Good Morning Scotland, and I began to get together. From the depths of despair, my life went through a complete change. We got married in 2004, in a wonderful village-hall wedding in Plockton."

That happiness was sealed on Monday with the birth of Hannah. She is Bateman's third daughter, and the first for Judith, who is 39. Her half-sisters are Eilidh, 31, and Lucy, 28.

"I am surrounded by girls; there are seven in the direct family, " says the proud new father. He is both slightly daunted by and keen to tackle the practical aspects of fatherhood at 55.

"Parenthood does change you. Although it is a bit like riding a bike, in that you don't forget, it was a long time ago, " he says. "I have matured in some ways, but I'm beginning to become an angry old man and I am not as patient as I was in my twenties.

"Already we've banished the computer to the basement and turned what was the office into a nursery. It's white and has a cot and looks lovely. We have a lot to look forward to.

"My working hours now mean that I am available in the mornings, and after my programme is finished on Saturday morning I have the whole weekend. Our visits to our local wine bar will be reduced. I know you can take kids to the pub now, but I'm not really into that, " he adds, in a comment which shows that, for all the warnings about the health and vigour of older fathers, the biggest difference between the over-fifties and the under-thirties is one of attitude.

There are technical advances, too. "The first time around, it was terry nappies with great big pins. I'm not sure about disposables. I don't actually know what kind of nappies we're going to use."

There is an ever-lengthening list of men fathering children in their fifties and sixties, but another significant difference is between those coming to parenthood for the first time and those who already have children from an earlier relationship. Bateman identifies with the latter - the John Simpson/John Humphrys model rather than the Gordon Brown one. "It is different for firsttime parents, where you are overcome by a complete sense of wonder. When you've had the experience before, it is a little bit different - but it is very exciting and a bit scary.

"Alison and I got married when we were 21 and then had our children, when that was what you did. Looking back, it seems we were almost blase about it, while nowwe have to work things out. Although I feel that I am a young 55, I am conscious that I am now going to have to be around for a generation and there is a bigger incentive to maintain my fitness. I do run, so I will try to keep that going."

THE genetic inheritance augurs well. Bateman's father is about to reach his 90th birthday, and the grandparents are "thrilled to bits." The new baby has been welcomed by the wider family. Judith is one of seven siblings, so Hannah has a wealth of cousins as well as her two half-sisters.

The genetic question is not frivolous. Though it's possible to cite Charlie Chaplin and other elderly (rather than simply mature) fathers as proof of men's continuing reproductive potential while women's biological clocks point to the end of fertility, new research this year found that babies of fathers in their forties and fifties tend to be less robust immediately after birth than infants fathered by younger men. A breakdown in the DNA in their sperm could put older fathers at higher risk of fathering children with conditions such as schizophrenia and autism.

You might think older fathers have gone from heroes to health hazards within a generation - but the reality is more human and much happier. Most mature fathers are simply worried about how to make the most of this precious second chance of being a dad. Dr Richard Woolfson, The Herald's adviser on parenting, says: "Maturity helps in most tasks, particularly parenting." He is equally upbeat about the energy gap and generation gap experienced by most older parents, as he adds: "Age is irrelevant, because a parent's job is to be a parent, not their child's pal."

Sleepless nights they wouldn't swap: celebrity mature fathers

David Jason (pictured right) His first child, Sophie Mae, was born in 2001 when he was 61. He complained about her waking up at night, but the actor said: "I love fatherhood and I'm blessed to have such a lovely little girl."

John Simpson The broadcaster was also 61 when his third child, Ranulph, was born in January. "No doubt people will be saying how disgusting it is that a man in his sixties should be fathering a child. Yet there will be all sorts of advantages to counterbalance the problems of age, " he said.

Rod Stewart The birth of his seventh child, Alastair, in 2005 inspired him to say: "The older you get, the more you can appreciate that you can still bring another life into this world."

John Humphrys (pictured right) Now 63, the broadcaster has a fiveyear-old son, Owen. His eldest son is 38. "To have a child in your life again at this stage makes you realise how wonderful the whole thing is, " he said.

Des O'Connor When his fifth child, Adam, was born in 2004, the singer was 72. He described the event as "a magical moment".

Michael Douglas The actor has two children with his second wife, Catherine Zeta-Jones. The first, Dylan, was born when he was 56 - 23 years after his first son - and his daughter, Carys, was born when he was 59.

Charlie Chaplin The actor was 73 when his youngest son, Christopher, was born.

Rupert Murdoch The media magnate's youngest two children were born when he was in his 70s. He has a total of six children.