This is Battersea Dogs Home (although since 2002 it has been called the Battersea Dogs & Cats Home), second only in local fame to the next-door power station.
The dogs home was founded in 1860, and moved to the Battersea site in 1871. This clock tower is obviously somewhat newer.
Information on the great work of the Dogs and Cats home can be found on their website at www.battersea.org.uk.
The proximity to the railway line can be seen in the photo below. However, south London is a jumble of railway lines, and these photos were taken from Battersea Part station which is on another route. I couldn't find anywhere to view the clock from the road.
These next few photos give a glimpse of the huge redevelopments that are going on in Battersea. The whole area is a crane spotters dream.