GRIFF Rhys Jones has forged a career out of being TV's Mr Cranky.

From grumbling his way around the world in a wooden vessel in the Three Men In A Boat series, to addressing his temper in Losing It: Griff Rhys Jones On Anger, the comedian is not shy of letting off steam.

But Rhys Jones, who made his name as part of the team on satirical sketch show Not The Nine O'Clock News, reveals a softer side in a new one-off BBC2 documentary, Burma, My Father And The Forgotten Army.

In it he learns for the first time the full details of his late father Elwyn's time as a medical officer in the country during the Second World War.

In particular, he discovers how his dad worked alongside soldiers from Asia and West Africa whose efforts were often overlooked during the fight against Japanese forces in Burma.

"History is extremely valuable in dealing with some of our modern-day egotism. We're just passing through and I think that's quite humbling," he says.

Rhys Jones, 59, who as a child was photographed wearing his father's army hat, was particularly moved to learn why his dad had never discussed his experiences during the war in any great detail.

"My father did tell us stories about funny things that happened, but the real truth was he was a modest man, unlike his son," he jokes.

"The difficult realisation for me was that they didn't talk because it was a time of terrible homesickness, boredom, discomfort, longing for it to be over, terrible conditions and fear."

As part of filming, Rhys Jones travelled to Wales, Ghana and eventually to Burma to learn more.

"The story is partly about my father but it's also about the West Africans, they are the forgotten story," he says.

"The British Army covered itself in heroics and praises, and it did do marvellous things, but 80% of the troops who fought in Burma were black or part of the Commonwealth, the Indian army, Gurkhas or West Africans."

While in Burma, he was surprised by what he discovered about his father's involvement in the war effort.

"I had imagined from everything my father had told me that he worked in a military hospital in India and then went to a field hospital in Burma, miles behind the lines," he says.

"But the first thing I discovered was that he had gone into battle with his troops. He fought in the jungle for six months. That was a bit of a shock."

This is not the first time Rhys Jones, who has a grown-up son and daughter with his graphic designer wife Jo, has delved into his family's sometimes upsetting past on TV.

In 2007, he discovered more about his Welsh ancestors in BBC1's genealogy programme Who Do You Think You Are?

Both programmes could have been emotionally draining, but the presenter sees his work as a valuable way of increasing his understanding of the world.

"I have been able to fulfil a further education for myself in doing these programmes," he says. "It's been an amazing opportunity."

That said, Rhys Jones is all too aware of how lucky he is to have had such a varied career. Not least because, until last year, he was able to film TV programmes with his much-loved dog at his side.

"My labrador Cadbury was the star of Rivers," says Rhys Jones, who brought the chocolate brown dog along for the filming of the BBC1 series in which he explored the ways rivers have shaped our history.

"I was completely bereft when he died aged 14. I'm still in mourning for him. People would stop me and the first question they'd ask, after the most learned disquisition on rivers, would be, 'How's Cadbury?"'

The dog may no longer be around, but the presenter hopes he will be for a good while yet.

"I went for a meeting at the BBC recently and they said 'People love to see you throw yourself off mountains and wade through streams'," says Rhys Jones, who is working on a new ITV series about Wales.

"I had to say, 'I'm nearly 60! Do I have to go on doing that?' and they said 'Yes!"'

While he is keen to carry on working, he doesn't want to overstay his welcome with TV viewers.

"Everyone's getting tired of me, you go around in waves, but I'd like to do more acting and performing if I can be allowed to do that."

Despite having been a comedian for 40 years, Rhys Jones finds showbusiness just as tough now as he did in the early years, but he's clearly mellowed with age.

He concludes: "I've had a great time over the last 10 years and have been happier than ever."

BURMA, MY FATHER AND THE FORGOTTEN ARMY, BBC2, SUNDAY