A source at Westminster City Council recently told me that two of the houses in the square have reported the presence of bats in Montpelier Square over the summer. Bats are protected species in the UK and any confirmed sighting of bats places an onus on the landowner to take account of their welfare in all future actions.
As earlier reported, we are currently applying for planning permission for our night-time lighting of the trees. If indeed we did have bats in the square then we would have to prove that the lights do not adversely affect them.
To find out if we had any heretofore unsuspected nocturnal denizens we commissioned a bat survey from Alison Fure (website). Alison has conducted bat surveys in the local area a number of times in the recent past.
Alison did not find any evidence of bats roosting in the square but she did still recommend that the lights be switched off in the summer months to protect any passing bats during the breeding season.
It is also worth noting that, using a light meter, she could not detect any change in ambient light levels with the garden lights on or off.
Her report: Bat Survey (PDF)