We weren’t expecting to get lost in the jungle. Not on a walk that began at the back of pub car park. As the Sunday lunchers headed into Castle Eden Inn for their roast dinner, our gang of four slipped around the back, between two garden fences, and into another world.

Trains haven’t run along the George Stephenson-designed Haswell to Hart railway in several decades, but there’s been life in the line for walkers, cyclists and riders since its conversion to a walkway by the major millennial clean-up that was the Turning the Tide project. Keeping a wary distance from the impressive (but toxic) giant hogweed, we followed the route to the first junction where we turned left and headed over farm fields. The waving green wheat made a peaceful place to sink down for a picnic.

Across Hesleden Road and into the outskirts of the village, we continued past St James Church onto the the approach road to the castle which gives the area its name. Complete with crenellated facade, palm house and Italianate gardens, this fancy 18th century gothic pile was built by local merchant and philanthropist Rowland Burdon, and housed the regional HQ of the National Coal Board before falling into dereliction (restored by private owners in 2004, the castle is now split into several properties). It’s the setting that’s the true stuff of fairytales however, namely the lushly wooded limestone gorge that lies beyond the castle gates.

Now a National Nature Reserve, this surviving remnant of Britain’s ancient wildwood is home to woodcocks and woodpeckers, roe deer and red squirrels, and more than 450 species of plants growing in the tangled, twisted landscape of yew, oak, ash and dying elm. As soon as we entered, the kids began to run, enlivened by the sense of magic and mystery that only a deep, dark forest can provide – and this one did, thrumming with the life-force of thousands of years of wild growth. So call it forest-fever, but when Lara skipped off the main track and onto a different path, we all followed.

Within five minutes, I was having flashbacks to jungle trekking in Borneo as we found ourselves battling through thick vegetation, vividly green with the fecundity of early summer, while the not-quite-an-actual-path underfoot grew perilously steep and slippery. When we finally found our route spectacularly blockaded by a gigantic chunk of landslipped cliff, we turned around and clambered back along the rocks of the dried-up riverbed  – folklore has it that these fell from the devil’s apron as he reneged on a deal to help build Durham Cathedral. Reaching ‘Devil’s Bridge’ after an exhilarating if almost surreal interlude, we rejoined our original route, more respectful than ever of our surroundings having glimpsed their true wildness.

The neutered greens of the golf course looked somehow equally surreal when we finally emerged back into the world of roads and reality, where for everyone else it was still just another Sunday, and where leisure didn’t seem to involve getting lost in the jungle. But where would be the fun in that?

Start/finish: Castle Eden Inn (postcode TS27 4SD, OS grid reference NZ423375)
Length: 3 miles / 5 kms
Time: 2 hours (plus more for picnic and, um, diversions)
More info: http://www.durhamheritagecoast.org/wp-content/uploads/sites/6/2015/01/castle-eden-web.pdf