Sleeping in a field. In early May. In Northumberland. When an old friend invites you to celebrate his 40th birthday by doing just that, what choice do you have?

It turned out to be better than OK. With a field just for our group of families and a load of other kids to run around with, our first camping trip of the year to Bellingham’s Demesne Farm left the girls pleading to do more. The cute resident calves and lambs helped, as did the late-night marshmallow toasting, and our new equipment purchases – tent carpet, super-thick double sleeping bag – made a huge difference to the cosiness. But it was the next day’s adventure that made the weekend feel like a week’s holiday.

After a grim few weeks, the weather finally delivered with blue skies and glorious sunshine (somewhat unexpectedly, hence the only downside which was having to spend the day in snowboots) so after packing up the tents while the kids staged a huge water-fight, most of the assembled families decided to head out on a walk. Conveniently starting from a car park just across the road, the route to the waterfall at Hareshaw Linn is a three-mile out-and-back walk that we’d managed only part of before, when it had nevertheless been an enchanting winter wonderland of icicle wands and frozen streams. In late spring, it was a new discovery.

The site of an ironworks in the mid 19th century, the first part of the walk passes the stone farmhouse that once housed the foundry offices, and the mounds climbed are made from the spoil of 70 coke ovens that once supplied it. Not that we wasted the kids’ attention spans on that information – the walk was to be the challenge. Four families set off, but the combination of blazing midday sun and uphill gravel path got the better of some of the smaller ones, and when we reached the clearing by the first small waterfall a few stayed put. The rest – by now a semi-feral, bare-chested gang of 5-8 year olds – had already bounded up the flight of stone steps and away. We kept pace, trying to take in the surroundings too as the path wound through beautiful woodland following the Hareshaw Burn below. Walkers have been following this trail since the 19th century, and it’s still one of Northumberland’s most well-loved – populated with native trees such as oak, hazel, elm and ash and alive with flora and fauna, it’s a precious and rare example of ancient (pre-1600s) woodland.

The gang forded six bridges, tackled some healthy climbs and descents, and stopped only once for rest (and to observe the rather captivating iridescent blue-black dor beetles making their way across the path). In a little over an hour, we arrived at our destination, a spectacular sight revealing itself only at the last moment. More commonly a Scots word for waterfall, thought to be a convergence of Old English ‘hlynn’ meaning torrent, and Scots Gaelic ‘linne’ meaning a lake or pool, the ‘Linn’ is just that, an exhilarating rush absorbed into a serene little basin, lushly lined with an abundance of ferns, mosses and lichens that have earned it a designation as Site of Special Scientific Interest. Most wonderfully, no-one managed to fall in. Apart from Lara.

We did however allow ourselves a little paddle before retracing our steps back to the start point – not at the waterfall, but beside the final bridge, an open spot with a small grassy verge and flat (though slippery!) rocks. A couple of coin-studded wish trees indicate that this has long been a popular spot – apparently a kind of bandstand once stood here, built by the Victorians for picnics, music and storytelling. That’s the sort of activity I would love to see revived – if only the weather were as reliably beautiful as this. At the very least, we could listen to the song written for this very place by local folk legend Kathryn Tickell. An inspiring place indeed.

The route: 3 miles, 2 hours. Start at the Northumberland National Park car park in Bellingham (postcode NE48 2DA, OS grid ref: 839 834, Explorer OL42).