Can't see the wood for the trees

Here's a photograph I'd guess was taken in 1963. It's of a small stream just to the north of Barnard Castle town centre called Percy Beck.

How can I date it so accurately? I used to play in this stream often as a child and one of the signal boxes operated by my grandfather was just to the right of the stone viaduct in the background - Barnard Castle West. In 1958 the woodland here in this valley was clear-felled and in 1960 they began to replant with the saplings you can see in the picture. In 1965 the railway was closed, and the signal post you can see on the viaduct was removed.

The trackless viaduct still survives but the woodland here has grown back tall again and you could walk under this bridge in summer and not even realise it was there. A lot of the stonework is covered in ivy and the new forest is mature - just within my lifetime.

I've included this picture here because for me it's a good example of how views can change so quickly - and often there's nowhere where that happens more obviously than around a railway.

Recently I returned to a good photo spot near a tunnel in Cumbria where I would photograph steam locomotives as a teenager. To my surprise all I could see was a wood! The lack of trackside fires since dieselisation, and changed maintenance priorities over forty years, had meant that the portal and track had completely vanished behind a screen of oak