I'm slightly confused by the "New Cross substation in Southwark" whilst the map immediately above clearly shows it in Lewisham[0][1].
Best I found was a page talking about vertical boreholes on Old Kent Road (opposite Commercial Way which is just inside Southwark) but nothing about a substation there on any page.
[0] Estimating off the National Grid map, it's roughly vertically centred between Lewisham and Greenwich DLR stations - absolutely not in Southwark!
[1] I feel like I'm going mad - the number of pages I found whilst trying to find the exact location that said the same thing under the same map is honestly discombobulating.
It’s easy to find on https://openinframap.org
If only the search engines had bothered to return that as a suggestion!
But yeah, that's the place on OKR I mentioned - just inside the Southwark boundary, not really New Cross. Nowhere near the dot that nationalgrid have on their map either.