Just think – if the Earth weren’t tilted on its axis, there’d be no seasons. No Autumn! Today is a perfect autumnal day. It’s just before sunrise. The sky is a clear pale blue, with a smattering of pink cloud above the eastern horizon. The well-trodden path runs between sycamores and rowans, northwards from Gilsland beside the River Irthing, which forms the boundary between Northumberland and Cumbria. It seems strange that some villagers live in one county, and others live in the other.

You cross the river by nicely regular, flat-topped stepping-stones, which appear intact initially, but, half way across, you see that one is missing. This merits a rude word. There’s no alternative but to step into the water – the first of many opportunities today to soak your feet. There is a natural law in Northumberland that requires every line of stepping-stones, however well constructed, to have at least one gap.

On the far bank, the path climbs to the grounds of the substantial Gilsland Spa Hotel, from which aromas of breakfast emanate. At this height, the sun comes into view, casting a deep golden glow backlighting the gravestones in St Mary’s church. You take the path signed Spa Well, which descends rapidly to the river. A carpet of deep brown and golden yellow leaves, mainly birch, conceals the mud beneath. Nearby is the source of the sulphurous spa water that made the hotel a popular location in the 19th century, and led to the construction of shops and a tearoom by the river (now long gone).

The Irthing Gorge is dramatic, with a craggy precipice at least 35 metres high, above its eastern bank. An extremely slippery footbridge takes you across the river into a tunnel of golden leaves. You traverse a bend in the river and cross it by another bridge, where several paths meet, deep in churned-up mud. Climbing uphill, you turn right behind a wood and then take a path running along a ruined stone wall, crossing a crude wooden bridge over a gurgling sike. Waymarking posts peter out, leaving you with no clear direction. Pushing your way through grasses and bracken still wet with yesterday’s rain, and stumbling into gullies, your trousers become soaked and your boots fill with water.

The rising sun transforms the wet surfaces into mist, which develops surprisingly quickly behind you. It’s like being stalked by fog. A fine filigree of spiders’ webs connects bracken stalks and mossy hummocks. It requires a lot of energy to cross this uneven, boggy terrain and progress is very slow. This is one of those instances when distances seem much greater on the ground than on the map. You sit for a while on a lichen-covered tree stump - the first of several sock-squeezing locations. It seems odd that you should feel so thoroughly wet on such a beautiful – and dry - day.

Past a Ministry of Defence sign that warns of an adjacent bombing range – just the thing for a countryside walk - you reach a signpost to Crammel Linn, a dramatic and noisy waterfall for such a modest river, that is even more impressive when the Irthing is in spate. From the hillside, you can see the river above the Linn snaking its way from the north-east, below the dense, dark coniferous plantations, their treetops turning gold in the autumn light.

The afternoon warms up and dries out your trousers somewhat, but you take the easy route back, along the road. Its hard surface is rather welcome. Nearby, an explosion is detonated as if to salute your departure.