It runs a comprehensive programme of volunteering holidays where,  for a nominal fee, members of the public can come along to some of the UK’s most scenic locations and pitch in to help build, repair and maintain anything from cycleways and coastal paths to storm drains  and drystone walls.

I’ve spent the day hauling rocks out of a river to help rebuild a bridleway washed away by a winter storm.

It’s hard, physical exertion, but with the camaraderie of my fellow volunteers, the gung-ho optimism of Steve, the local warden, and the calming surrounds of a bluebell-carpeted forest, time flew by.

Between the 12 of us (plus Steve and team leader Carl), the site now has a brand new drain diverting a stream away from the bridleway, as well as a carefully crafted drystone wall holding up the river bank.

Here in Britain’s south west, the craft of drystone walling  is somewhat different from the horizontal style commonly seen in the rest of the UK, such as those snaking across the Lake District and the Yorkshire Dales,  for example .

On Exmoor, flakes of stone are slotted together vertically in planes, the resulting wall proving surprisingly sturdy. The trick is to find big, flat stones that fit together — no mean feat when they’re 50cm across and made  of granite.

Not only are we employing a centuries-old building technique, we’re doing it the old-fashioned way — with blood, sweat and toil.

“Volunteers are the life blood of the National Trust,” Steve tells me, eyeing up a semi-submerged boulder. “We wouldn’t be able  to do this kind of job without them — it’s that saying: ‘many hands make light work’. They’re an enormous help.”

“I think it gives people a sense of satisfaction,” Carl muses later, chewing his lunchtime chocolate bar. “We get volunteers from all walks of life, many of who spend their working days behind a desk.”

“To come together and build something that will last for years to come — there’s something very exhilarating about that. Plus you get to quite literally make your mark on some of Britain’s most glorious countryside, all in the hands of a local expert.”

As I retrace the winding cliff path  in the fading light, I can’t help but agree. And if making a difference weren’t rewarding enough itself, there’s a dinner of roast chicken followed by an evening of card games and banter awaiting me.