Site: St Marks, Kennington (2 memorials)
SW9, Clapham Road, St Marks Church
The church's website has a good history page with more information. The church was built in 1824. Oval History has a photo of the ruins left by WW2 bombing.
When we visited in Spring 2015 the church grounds contained a weapons bin, "Get a life, bin that knife", which it's difficult not to interpret as a comment on the locality.
The section of the common now occupied by tennis courts and a football pitch were added following slum clearance in 1921. The section, to the SE of St Agnes Place is known as the Extension, added in 1970s.
British History On-line gives the site of the Kennington Common gallows as "Part of {the Common}, including the site of the church and burial ground and the triangle of land between Brixton and Kennington Park Roads".