Clarendon Square, St Pancras - 1851

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I have people living at #29 Clarendon Sq in 1881 and #39 earlier.  By 1891, they have moved, so I think they must have moved because it was torn it must have been torn down between 1881 and 1891. 
It was part of a major development having to do with Baron Somers and his land.  It quickly became a slum, from my understanding. 
See http://www.kingscrossvoices.org.uk , and click on the history section, and read through the origins of Somers Town
and
http://en.wikipedia.org/wiki/Somers_Town
I haven't checked, but I wouldn't be at all surprised if you can find some good information on this housing development at the Guildhall.  It seems to have been a significant undertaking - maybe even photos if really lucky!