Habitat = wall in urban street
No interactions present.
'toung specimen' in the identification notes should of course read 'young specimen'!
I was just looking it up, thought it was yet more botanical jargon!!
How to take close-ups with cheap phone and hand-lens:
Field Guides for Budding Botanists:
looks like A. adiantum-nigrum to me...
Thanks for the confirmation Chris and for the extra ID tips.
Lat/Lng: 51.6208, -0.017
OS grid ref: TQ373931