I don’t remember why I was there, where I was going or what I was doing, but it was high summer because there were swallows and martins on the overhead wires. Beyond the level crossing, behind a high and wild robust hedge, peaked the eaves of a long since deserted grand house – there was a view of a gable and smashed windows from one point along the pavement, a story in a glance – and all about this there were swifts nesting, speeding and screaming overhead. The weight of the air and the sun. And here I was stopped at a line I thought long since closed down.

I didn’t like stopping my car, a wreck of a thing it was, a cheap tin box filled with eccentricities and required knacks, which could not idle reliably. I had to keep the accelerator revving constantly. And these gates shouldn’t be shut. The line was disused and abandoned I thought. Pink valerian raging either side of the road. Laburnum and buddleia up and over the rotting yellow-white fence posts and ruined sheds, a jungle covered in bumblers and honey bees, peacock and tortoiseshell butterflies. No-one behind me or waiting on the other side. But the gates were shut.

I let the engine die.

We used to do this. Go further back. We used to do this, in Dad’s car, the Lincoln line, up near the power station. Lights flashing side to side. Guessing from where the train would come, left or right. Straining to hear. Asking Dad to switch the engine off. And then that rush and push and the wheezing bellow of the loco (Type 47s or 31s, double-headed sometimes, filthy, burping muck and fumes) as it rattled rhythmically past. “Count the hoppers,” Mum shouted over the din.

Twenty seven, twenty eight, twenty nine…and the guard’s van. I still say that, even now, even without guard’s vans. The noise receding swiftly, like the sound of a wave dying, pulling the silence in to replace it. And the rails sang after.

I can hear this loco, trundling slowly, from the right, wheels clunking over the gaps. It passes, a 37, the old English Electric Type 3. At that point I remember thinking we used to have to go spotting in Sheffield to see those. Truck after truck followed. All empty.

And then it’s gone. And the wave goes like before, swallowed by the air. The rails sing gently again. And there are swallows and martins. And the swifts.

And the gates, do they lift or open, swing to the side? I don’t remember. I just remember the hole in the quiet, and the quiet, and then the birds.

It’s the only train I’d ever seen on that line. Thirty years ago, but the memory of it surfaces every time I pass the same spot. Even after the track was lifted and the idea of reopening was abandoned. Even after they laid concrete and allowed buses to use it. After all that, I still see the sand-streaked 37 and the empty trucks.

My friend Ray and I spoke about the line a couple of times. I wanted to walk it, from Cambridge to St Ives, see familiar places from a different perspective. That secret path that rail tracks make, holloways made by toil and memory and the knowledge of the lost. There used to be a line here. Like the way through the woods, but filled with steam and endeavour and all those daily grinds and now nothing. Well, not nothing. The gap encroached by nature. But those tunnels in the air, in the fields, in the hedgerows, down there people slipped.

That was the idea, at least that was the idea I had. New views, old acquaintances. I think he humoured me for about two pints with that one. I hung on to it though, but never made a move to try it. Once the rails came up and the busway was laid I lost the need to try. After Ray died I pushed it away even further.

But I cross it every day, see it, know it’s there. A line tied, and pulling.

The railway buildings along its path, half a dozen village stops, have mostly been repurposed into private dwellings, although Histon station, for years the focus of a community project to resurrect it, sits abandoned and shuttered now, graffitied and knackered. It’s still resolutely a station, still has those daggered fascia boards, that grey-brown brick, the unmistakable and undimmed architecture of the Victorian railway.

The guided bus pulls up and takes us to St Ives. I know the places passing by, but not these views. Stupidly, I am overwhelmed. I’m making connections and then dropping them with disconnects. A wave of realisation, and reappraisals of how things fit in. How the jigsaw works. Through a long cutting, a call back to other journeys, shifting the map around in my head. Farmhouses and windmills, roads barely travelled. I am moving my head around like a child on a funfair ride, trying to understand how all of this works. How it fits together.

At Fen Drayton Lakes, a great nature reserve pulled, rescued and moulded from unused and reclaimed quarries, the penny drops about the train from thirty years ago. Sand-streaked and dragging the empty trucks. Now there are egrets here, bitterns if you’re quiet. In the far distance a buzzard drops behind the tree line.

The bus pulls in past the old St Ives railway station (now an accountants) and into the town, breaking the bounds of the old railways. Back into reality.

There’s a market on, little stalls of veg and plants and cheese and bread. I’ve not been here in years. I’d decided that I didn’t really like it, but it seems ready to rethink that. It’s small and bustly and has two tremendous churches. There is a quayside, swans, an ancient arched bridge with a chapel halfway. Across the river the flood meadow is covered in gulls. A heron stares across the river towards the town.

Over the marketplace, past the church spires and between the beech trees, a pair of red kites glide, playfully, spring-filled and unhurried, bellies reddened in the sunshine.