Sir James Chadwick: 1893 - 1981
Awarded the Nobel Prize in Physics in 1935 for the discovery of the Neutron. This discovery was named as one of the greatest scientific achievements of all time and considered by Time Magazine as one of the most important milestones of the 20th century. Over the next several years, teams of researchers in several countries bombarded every known element with neutrons and recorded hundreds of new radioactive isotopes.
Chadwick was key in connecting British scientists with the Manhattan Project. He was close with Manhattan Project's leader General Groves, and worked with British counterparts to determine that Americans had oversetimated the amount of U235 needed to achieve a chain reaction (critical mass). Chadwick and many of Britain's other leading physicists joined to form 'the Maud Committee', and produced a report saying that a nuclear bomb could be ready by 1943.
He helped draft agreements to provide uranium for the Manhattan Project,
maintained the morale of British scientists during their time in America,
and was responsible for British observers being present at the bombing