The most expensive letter sold at auction was sold for US$6,098,500 (£3,964,025; 4,634,860€) on 10 April 2013 by Christie’s, New York, USA, for a letter written by Francis Crick in 1953 to his son Michael Crick, outlining the revolutionary discovery of the structure and function of DNA.

In the seven-page handwritten letter ‘Secret Of Life to his 12-year-old son, Francis Crick describes his discovery of the structure of DNA as something “beautiful”. It includes a simple sketch of DNA’s double helix structure.

The letter was sold to an anonymous buyer.