Polygamy costs

English Heritage has placed a blue plaque on the former London home of crystallographer John Desmond Bernal.

Bernal was a Marxist and one of the first to write about science in a political context. He was also a personal friend of Pablo Picasso, who painted a mural in his flat - now on display at Birkbeck College, London.

Professor Bernal believed in non-possessive relationships and maintained three households with his wife, two mistresses and four children. He would be hard pushed to afford that on today's salaries - even with a London weighting.