Tory blog: London Spin, then the Hackney Post (the newspaper of City University post graduate students - which is now back in action after a year off?) and Press Association - reported the appearance of David Cameron in Hackney South.
But why Hackney South? The last time David Cameron and Hackney were so closely linked was back in January when when some of his giant posters were defaced: Hackney responds to David Cameron
Otherwise, as far as I can see, Hackney's Conservative group hasn't got any South Hackney-based councillors and its been a Labour seat since it was created in 1974.
May be it has got something to do with Hackney South Conservative candidate Simon Nayyar: http://www.simonnayyar.com or was it just a suitable venue?