I love the way that London’s green and wild corners are revealing themselves to me little by little.

One day, as I was jogging around Finsbury Park, I noticed a steady stream of walkers and cyclists seeping in and out of a narrow passageway above a railway bridge. Curious, I crossed over the bridge and saw something I did not expect to see: a woodland path winding into the distance.

This greenway, known rather humbly as Parkland Walk, follows the course of an old railway line, which once ran from Finsbury Park to Alexandra Palace. The track travels through a region of North London called the Northern Heights – a name that does a better job of capturing the mysterious charm of the place – and, at 2.7km long at its longest stretch, it is London’s longest linear nature reserve.

It took me five years to discover Parkland Walk, and each time I walk or run it, I discover something new about it. On my third or fourth visit, I paused for breath beneath the railway arches at the former Crouch Hill Station, and happened to look up. That was when I first saw The Spriggan, a folklorish creature carved in stone, emerging from the shadows and peering down at me through trailing ivy fronds. The sculpture was created in the mid-1980s by local artist Marilyn Collins and is said by some to embody the spirit of the way and to protect it from harm.

It would seem that it works…

Having escaped development for housing in 1978, Parkland Walk has twice since been threatened. First, in the late ’80s, when the Department of Transport proposed the construction of a 6-lane motorway along its length and again when Haringey Council’s conservation unit was axed in the early ‘90s. On all three occasions, the local community united to ‘Save the Walk’, stirred up perhaps by the spirit of the Spriggan….

I walked the line again a few weekends back. And I made fresh discoveries, in part thanks to following a tree trail created by the Friends of Parkland Walk on the free TiCL app.

The spring sunshine had brought out the people of Haringey in force. My walking companion and I jostled for elbowroom with joggers, cyclists, dog walkers and families. I wondered how many of them knew that the way had been almost lost three times.

In the fifty odd years since the rails were removed, hundreds of trees have sprung up along the banks. Most, including the oak, ash, hawthorn, cherry and sycamore, have arrived naturally, while others such as black poplar and hazel have been planted, and more others, including a fig, are back garden escapees.

One sycamore stands out from the rest. It appears to be propped up by an old brick wall where a railway building must once have stood. Whoever removed the building was careful to leave behind part of one wall so as to avoid disturbing the tree’s root system, which has become enmeshed with the brickwork. Each time I pass, the wall and roots sport a different graffiti design, and that March day was no exception.

But the way is not entirely wooded. At times, thanks to the work of the Friends and The Conservation Volunteers (a longstanding member organisation of The Tree Council), the trees give way to open acid grassland, wildflower meadow and scrub, with each habitat supporting its own array of wildlife.

Until that day, I had only ever walked the first section of the route – Parkland Walk South – but the time had finally come for me to discover the second leg, Parkland Walk North, which leads into the grounds of Ally Pally.

We linked up these two green corridors with a walk through Highgate Wood – the largest of Haringey’s four ancient woods, a remarkably peaceful spot and surely one of the wildest corners of central London.

Walking the line and the woods, I found my mind running along another line – the proposed HS2 railway line – and thinking of other woods. According to the Woodland Trust – another of The Tree Council’s members – 63 ancient woods are threatened by the current plans for phase 1 of HS2, either with direct loss or damage through disruption, noise and pollution. I couldn’t help but think that these woods could do with a Spriggan to watch over them.

Parkland Walk North was much quieter than its counterpart. Perhaps, it’s not such a popular shortcut. Or perhaps, it simply takes longer to discover.

The tree trail reminded me to look out for wildflowers – more than three hundred species have been recorded along Parkland Walk. I spotted cow parsley and wild garlic growing amongst the remnants of railway signals and atop a mossy log a patch of lesser celandine was glowing in the spring sunshine.

Nearing the end of the walk, we passed over a seventeen-arch viaduct, and paused to take in the spectacular views eastwards and southwards over London.

Northern Heights indeed.