A zipwire adventure in Eryri (Snowdonia) with Matthew Rhys

We’re standing on top of the mountain overlooking Blaenau Ffestiniog. It’s one of those perfect, cloudless days when the views don’t know when to stop. The pyramidal summit of Yr Wyddfa (Snowdon) is one of dozens of peaks that jab the horizon. Below us lie the old quarries and spoil heaps of Blaenau.

The actor Matthew Rhys surveys the scene. He is wearing a red jump-suit and a majestic beard, cultivated especially for a role in a medieval drama, in which he plays Gruffudd y Blaidd – The Wolf – a 14th century Welsh warlord. Grrr. He’s played other Welsh heroes – Dylan Thomas, notably, in the 2008 film The Edge of Love – and cracked Hollywood in the drama Brothers & Sisters, from which his career has never looked back.

Today is his last in Wales for six months. He’s catching up with family. A whole tribe of them and their friends have gathered in Eryri (Snowdonia) to eat, drink, laugh, dandle babies, jump around on subterranean trampolines, fly over abandoned quarries. Muck around, basically.

So this is why we’re standing, in red jump-suits, on a Welsh mountain in Blaenau Ffestiniog. The town is at the geographical heart of the Snowdonia National Park and yet, when you look at the road map, it’s a little grey island in a vast green ocean. When the Park’s boundaries were drawn in 1951, Blaenau’s still-booming slate quarries lacked the requisite chocolate-box charm, and so it was excluded. Inside the enclave, the slate mining has mostly vanished, leaving behind an otherworldly landscape of jagged edges that is startlingly impressive, in its own way. They’re talking about re-drawing the National Park boundary to include the town. Not everyone is bothered. Some of the locals didn’t wait around for others to decide if industrial ruin could be repackaged as industrial heritage. They thought, 'Nah. Let’s do it ourselves.' (In Welsh, though – it’s the first language of practically everyone here.)

A group called Antur Stiniog carved mountain bike trails into the quarried hills. Another local, a cheerful ex-Royal Marine called Sean built the world’s fastest zip wire, Zip World Velocity 2 – a mile-long, 100+mph (160kph) monster – over a quarry at nearby Zip World Penrhyn.

Back in Blaenau, his team made the world’s biggest zipzone: four parallel wires, set over three different bits of mountain and moor. Then they added an underground course of zip lines, rope bridges, obstacles and tunnels. Zip World now employs over 350 locals, and is building zip wires all over the world, including Zip World Tower, in Rhigos, South Wales. 

We’re doing the one called Zip World Titan 2, (which is part of Zip World Llechwedd) whose starting point is at the apex of this mountain.

We’re not alone. Groups of mountain bikers arrive by the vanload to hurl themselves down the black runs of Antur Stiniog, whooping in a rich variety of European accents. A few pause to watch Matthew, his sister Rachel and her children, Harri and Gwen, clipped on to their zip wires. They launch into space, all four in parallel, heading for a landing zone that’s a kilometre away. Matthew is humming the James Bond theme.

Well, you have to, don’t you? You do feel it’s like a few experiences rolled into one. You get the astonishing view, the ‘I’m flying like a bird,’ and ‘I feel like James Bond and I’m parachuting into Blofeld’s lair.

Didn’t you audition for the part of Bond once?

'Ah, yes. It was just before Daniel [Craig] got it. It wasn’t just me, they auditioned all my mates, including Ioan [Gruffudd]. You had to read a bit from Casino Royale, and then the first question they asked was, ‘What would you do differently with Bond?’ It sounds daft, but it was the last thing I expected. It’s a winning formula, why change it? I didn’t know what to say. Um… give him a limp? An eye-patch? A pet parrot? I know, let’s make him Welsh...' He didn’t get the part.

The Zip World people, meanwhile, are rather good at what film people call a 'reboot'. At Blaenau Ffestiniog, they found themselves wondering what to do with a huge underground slate cavern. We know, they said. Let’s bung a giant trampoline in it. No, let’s go for four giant trampoline-like cargo nets, one of top of the other, connected by nylon snakes and ladders. With some trippy coloured lighting. It’s called Bounce Below (also part of Zip World Llechwedd) and Matthew and family spend the best part of an hour moon-walking around its oddly womb-like interior.

The kids pronounce it even better than the zip wires. Matthew is enjoying himself hugely, too. But then, he’s the sort of chap who likes an adventure. 'l try and do an adventurous horse trip every year,' he says. Excuse me? Horse trip? 'My dad’s from a big farming family in Mid Wales. We were shipped off to my uncle’s farm at holiday time, and we used to knock around on ponies. After I left drama school I started to get into it again. I’m interested in the great horsemen and women of the world. The Mongolians, the Bedouin, the Gauchos. When you’re travelling with them, it’s a great insight into a country.' It works the other way, too. When he’s filming in Wales, Matthew always gives the cast and crew the full Welsh experience, with both barrels. Put it like this, Keira Knightley and Sienna Miller will never forget their night out in Aberaeron.

You talk to the Americans, and they’re amazed at how you can get anything within a couple of hours’ drive. You want a huge beach, true mountains, a great coast, castles. It really can offer everything. Then you come here and find the landscape is lending itself to… this.

He holds a hand up to the blue sky. On cue, four more zip wires scream overhead. We laugh. It’s good to be home.

Exploring the outdoors is fantastic fun, but please read up on the risks and make sure you are prepared.

• Find safety advice for exploring Wales' National Parks and safety tips for staying safe on the Welsh coast.
• Visit AdventureSmart.uk for information on how to stay safe whilst exploring Wales.