‘They would have cut down the ancient woodland and planted western hemlock or Douglas fir, probably,’ said Beverley. Because back then you wanted a tree with a nice straight trunk that grew fast and was easy to manage. Then, in the late sixties, it began to occur to people that perhaps there was a bit more to reforestation than just planting a ton of trees. By the early 1980s someone had invented the word biodiversity and rural landowners, who up until then had cheerfully been industrialising the landscape, were told to start putting it back the way they’d found it – in fact, better than the way they’d found it, if you don’t mind.

‘When the National Trust took this place over they probably designated it a PAWS,’ said Beverley. Which meant Plantation on Ancient Woodland Site, which led to the next question – what the fuck is an ancient woodland?

‘They call it the wildwood,’ said Beverley and, according to the men and women with serious beards and slightly windswept hair who make it their business to know this stuff, it used to cover pretty much most of the island of Great Britain. Then, 6,000 years ago, farmers turned up with their fancy genetically modified crops and started clearing the forest out. And what they didn’t clear got eaten away by their artificially mutated cattle, sheep and goats. By the Middle Ages most of it was gone, and Britain entered the Napoleonic War desperate for timber.

‘Why do you know all this stuff?’ I asked.

‘It’s all anyone involved in working the countryside ever talks about,’ she said. ‘That and the vagaries of the EU subsidy regime and how evil the supermarkets are. Anyway, ground cover has a critical impact on water tables and flow rates. so you can bet we all take an interest in that – even Tyburn, who’s pretty much a storm drain from one end to the other.’

Beverley pointed out the trees that had been left standing when the area was cleared. A long strip of them went along the river bank and beside the footpaths. ‘That’s deliberate. Those are remnants of the ancient woodlands,’ she said.

‘And the weird bit?

‘It’s the timing,’ she said. ‘You don’t just charge in and clear ten hectares of commercial forest – which apart from anything else is worth a ton of money.’ So normally you wait for the current crop of western hemlock or Douglas fir or whatever to mature and then you cut them down and replant with historically appropriate broadleaf trees. Forest management not being an industry for people with a short attention span.

But according to the dates we’d seen on the sign, the trees had only been halfway to maturity before they were felled. ‘That would have been a serious loss of revenue, and I doubt the Forestry Commission would have liked it.’

‘And that’s what’s weird, is it?’ I asked.