Clock

I did some research on the clock manufacturers. It seems that the company was originally Gillett and Bland which later became Gillett and Johnston https://www.gillettjohnston.co.uk/ based in Croydon. I think this clock is probably from 1850s. It still works. 

The estate agents in this building informed me that they are renting from the local council and, so, the clock is maintained by the local council.