On 7 Feb, 09:36, "Martin J" wrote:
Any sensible suggestions, like where one might innocently take some photos
or even manage some video footage?

I'd take an all stops Welwyn Garden City train north from KX and pick
the first local station I liked the look of. Very few of them are
gated or staffed (beyond someone hidden in the ticket office).

If you don't fancy that, go to Caledonian Road tube, turn left, and
there's a clearish view of the line coming down the ramp from Holloway
Road bridge (which it goes over) to Caledonian Road bridge (which it
goes under).

Most footbridges and road bridges are useless because of the high
sides requirement above overhead wiring.

U