Martin Clunes is back on his travels - and his latest quest takes him island-hopping around the USA from west to east. With plenty of surprises along the way, he fills Gemma Dunn in on his ambitious trip.

Martin Clunes has made no secret of his interest in island life.

Over the last decade, the Doc Martin actor, 57, has made it his mission to visit some of the most remote places on the planet - from navigating the islands of Britain in 2009, to embarking on an epic journey around Australia's coast as recently as two years ago.

Next on his hit list: America.

"It just seemed like the next big thing, a natural progression from Australia," he says of his decision to explore some of the thousands of islands which also fly the stars and stripes. "But I'd no idea it was going to be as fabulous as it was. It's so interesting - not what you'd expect," he admits.

Covering 10,000 miles, Clunes' ambitious trip takes him on a voyage around America's shores - from Hawaii's islands of fire to Alaska's islands of snow and ice, and from California's secret marine paradise (including an impressive sea lion colony!) to the people playgrounds off the New England coast.

"Everyone has an image of America: A land of big shops, bright lights and asphalt highways stretching right across the continent," he muses. "But there is another America - and I set out to find it.

"I saw nature at her most spectacular, encountered the animals that inhabit these far-flung places, and met people who live in their own sea-bound worlds," he lists, having filmed four tours over three months. "Each island has its own identity and its own unique story."

Of the four-part documentary, he continues: "You just get a very different slant on a nation from its islands; you get people living with island challenges, and doing them in an American way."

First up on Clunes' itinerary were the lush, tropical climes of Hawaii. But his visit would look beyond the state's image as a tourist paradise and instead into the havoc wreaked by advancing lava fields and smoking craters.

In fact, the London-born star arrived just as one of the most devastating eruptions in Hawaii's recorded history was hitting worldwide news. Lava from Kilauea, one of the world's most active volcanoes, destroyed homes and sent residents fleeing in its wake.

"We were all ready to go and then the eruption happened, and it continued while we were there!" he shares.

"I proposed to Philippa (Braithwaite, his TV producer wife) in Hawaii 23 years ago," he continues. "We flew over it in a helicopter, and you could see cracks and red lava and a plume of gas then. But this time, these fissures were erupting left, right and centre."

"It was extraordinary!" he says of entering the danger zone. "When you see it from above, it's out in the wild, incredible and impressive; but when you see infrastructure up close, like a road just cracked and the yellow of the sulphur and gas coming up, it's just bizarre."

But that's not the scariest moment Clunes encountered.

First there was a hair-raising roller coaster ride ("It was made of wood and I always think that the top of my head is going to come off because I'm taller than everyone else"); special access to the very top of the Empire State Building ("I just don't like heights"); and finally a flight in a 1920s biplane.

"That was an expensive day's filming - we had a helicopter to film the biplane and we were going over the San Juan Islands in Washington state," he recalls.

"The minute we took off, we hit turbulence and we had no roof!"

Clunes admits he was pleading 'Don't go higher, don't go higher!' - even though the pilot couldn't hear him.

"I'm not good with heights!" he explains. "It started when my daughter was born, actually. I didn't think I was bothered before that. And then you worry about all sorts of things, you become more cautious. Or at least I did."

Clunes, who lives in Dorset, where he runs a farm with heavy horses, had visitors while filming - his wife and daughter, Emily, 20, joined him in Virginia for the annual Chincoteague Island Pony Swim.

"Every year, a load of wild ponies swim from Assateague Island to Chincoteague Island with cowboys herding them along through the water," he says.

"It was started by the Chincoteague Fire Company to raise funds, (but) it has snowballed, and the whole island bases the identity which it projects to the outside world on that one day."

"We were in heaven watching the ponies," he confesses. "I wasn't tempted to buy one though - we have enough horses at home!"

So just how does he readjust to home life after such lengthy stints away?

"Yes, there's that decompression, it happens after any job," he confides. "It's always long hours and it's all about activity, and although there's always something to do at home, I try not to get stressed."

"I had a very fantastic but busy year, last year," reasons Clunes, who most recently starred in Vanity Fair and Manhunt, and will next feature as the lead in BBC One sitcom Warren, before filming commences for the ninth series of Doc Martin.

"So I'm thinking, 'Don't get stressed about the farm, don't worry about that fence, just take things slowly'."

Is there anything he would like to do?

"No. I mean, I know there's more to do and it will be great, but I don't need to play Macbeth," he says with a smile.

"But you never know - I always thought I didn't want to do another sitcom, but then Jimmy Mulville sent me the Warren script," notes Clunes, who is best known for his starring role in Nineties classic Men Behaving Badly.

Clunes summarises Warren as "a vile driving instructor opportunist, rude man, living in Preston" and adds: "He was really good fun to play; I just like playing horrid people, it's liberating."

As for another island series: "We're going to do the islands of the Pacific next," he says excitedly.

"I think it would be in 2020, if it gets picked up, because that won't be a Doc Martin year.

"That's my pension plan - to be the island guy."

Martin Clunes: Islands Of America will premiere on ITV on Tuesday, February 5.