‘Are we nearly there yet?” The much-dreaded phrase came loudly from over my shoulder as we edged nearer to the coast. In fairness it had taken longer to arrive than I had anticipated. This was, after all, the final stretch of our two-day circular walk around Exmoor national park. I took a deep breath, sighed, and turned to my 68-year-old father.

“Yep, nearly there dad,” I said.

We were on a self-guided walking weekend trying out the National Trust’s newest kind of accommodation – the camping bothy. Essentially stone tents, these simple overnight shelters offer walkers sleeping platforms, running water, a proper toilet – and that’s about it – for a mere £20 a night (for sole use – up to four people). It launched its first camping bothy, at Peppercombe, in 2015.

It was so popular – fully booked from June until August last year – that the trust has opened two more. Foreland is a former stable beneath the village of Countisbury; and just this month, Heddon Orchard bothy, a former apple store built in 1867, opened just west of Martinhoe. Now it’s possible to walk between the two bothies on a newly devised 21-mile circular route (nine miles on day one, 12 miles on day two), for a two-night getaway entirely on foot.

“We’re lucky in west Exmoor to have that combination of wilderness and convenience,” says Hywel Lewis of the National Trust. “You can be walking on wild cliff edges minutes before you’re stuffing yourself with a cream tea, so we can make a little bit of an adventure accessible to a wide variety of people.”

As a wilderness lover, I’m used to roughing it in real bothies (where you can’t book and have to share the space with strangers) and hiking until my feet hurt, but to test its suitability for those with less of an appetite for pain and unpredictability, I invited my recently retired dad along.

“Did you print off the map?” I asked him as we rolled into the car park at Countisbury.

“Yes, but there are some bits missing.”

I looked at the paper he pulled from his rucksack: it resembled a kind of pictorial Morse code. Turned out the ink in his printer had run out.

Several false starts later – including a worry about whether we’d locked the car (it turned out to be self-locking) – we set off through an old churchyard and out on to the top of sea cliffs. My misgivings disappeared as fresh air filled my lungs and we both smiled as we turned left on to the well-marked South West Coast Path.

The going was smooth, with coastal views that kept our eyes busy. We stopped for a snack in Lynmouth before I led us up the steep hill alongside the funicular train. (I only found out halfway up we could have cheated and taken it, but decided against telling him.)

Shortly after this we entered perhaps the best part of this coast – the Valley of Rocks, where fossilised bedrock has been exposed by crumbling cliffs and weathered and cracked into fortress-like protrusions.

Distracted by them and views over the Bristol Channel and Wales beyond, the miles flew by. After passing the old monastery at Woody Bay and chasing sheep off the path at Highveer point, we were ambling towards Martinhoe and our pristine-looking bothy as the light was beginning to fade.

Once we had fathomed out the Crystal Maze-inspired contraption to release the key with a code the NT had sent us in advance, we were in.

The small room smelled of fresh paint and newly cut wood. To one side was a little L-shaped bench, and across the room stairs to led to a mezzanine sleeping platform. The toilet hut was still being finished when we visited so we were given a key to the NT ones along with … staff showers.

“And I thought we would be roughing it,” dad laughed as he returned from freshening up.

That night, by head torch (there is no electricity in a bothy), I made us camping meals and hot chocolate on my stove before we retired to our sleeping bags. Dad fell asleep fast, and I was left to study the map for our inland route the next day.

The sound of rain tapping on the window woke us the next morning. I worried it would put dad off, but after his first night in a bothy, he walked with the confident swagger of a veteran outdoorsman. He laughed as we got hailed on, talked like a walking stalwart when we met a bedraggled couple turning back, and steadfastly refused to take a shortcut when we became befuddled over a right of way across farmland.

As we followed the ridgeline on the hills above Myrtleberry Cleave, everything was sublime. The sun broke through the clouds and from our vantage point we could see where we’d walked the previous day, giving a real sense of accomplishment. By the time we reached Countisbury, dad was resolutely leading the way; I began to think I’d underestimated him.

All that remained was to find the bothy, half a mile away on the headland. As we neared it, the wind whipped into a frenzy, the ground became tussocky and rain started to fall. It was then I heard him utter the words I’d been dreading. So it was with relief that I finally spotted Foreland bothy’s roof.

“Shall I get the car and we’ll go and eat in the pub?” I asked. He beamed.

Sitting in Countisbury’s Blue Ball Inn, eating our well-earned hot meal, I looked over to dad. The National Trust is aiming to develop even more bothies here, I told him, and it wants to encourage Somerset and Cornwall to do the same. So it looked like more bothy-to-bothy adventures could be on the cards. What did a novice like him think?

“Again, again,” he laughed. It was going to be a long drive home.

• Accommodation was provided by the National Trust. Heddon Orchard bothy and Foreland bothy both cost from £20 a night (sole use) and sleep up to four. Guests need to pack as though camping, minus the tent