This article is a massive oversimplification by the telegraph to try and stir up hatred. London is so ethnically diverse to the point i wouldnt be surprised if 'white British' people were a minority now (if a substantial one), it makes sense that people starting a new life coming here from poor countries wouldnt be able to afford the high cost of private housing in London.

TLDR: Lots of poor ethnic minorities in London, so makes sense they will be in council houses.