The number of foreign-born residents living in England and Wales increased from 4.6 million in 2001 to 7.5 million in 2011 - 13% of the population, census data from the Office for National Statistics showed.
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Arthur Simpson-Kent, 48, admitted killing Ms Blake and their sons according to his lawyer.
Two brothers have been arrested on suspicion of murder after their parents were found dead in their own home over the weekend.
The first man to be convicted of murder on the basis of DNA evidence should be moved to an open prison, according to the Parole Board.