On 2015\10\07 12:58, wrote:
Le mercredi 7 octobre 2015 07:56:08 UTC+1, Roland Perry a écrit :

I can't see that, could you zoom in on Google Maps and post a short
link?

I have no idea how to do that. Does the following work:

https://www.google.com/maps/d/edit?m...ZM&usp=sharing

Not for me.

Just North of the Tennis Courts (that are in use) a some way to the West of the reservoir and a little to the SE of where the Parkland Walk begins.

That sounds like it's on the former alignment of the line to Highgate.
Are you sure it's not an abandoned viaduct support?