The division of the MAUD Committee at Cambridge was jointly led by Bragg and Cockcroft. It included Brestscher, Feather, Halban, Kowarski, Herbert Freundlich and Nicholas Kemmer. Paul Dirac assisted as a consultant, although he was not formally part of the team. On 19 June 1940, following the German invasion of France, Halban, Kowarski and other French scientists and their families, along with their precious stock of heavy water, were brought to England by the Earl of Suffolk and Major Ardale Golding on the steamer . The heavy water, valued at £22,000, was initially kept at HM Prison Wormwood Scrubs, but was later secretly stored in the library at Windsor Castle. The French scientists moved to Cambridge, where they conducted experiments that conclusively showed that a nuclear chain reaction could be produced in a mixture of uranium oxide and heavy water.