After completing his studies at Manchester he spent two years as a research associate at Cavendish Laboratory in Cambridge. He was a Fellow at the University of California, Berkeley until 1960. While at Berkeley in 1960, together with Andrew Sessler, he made the prediction that liquid helium-3 would experience superfluidity, flowing without friction, at temperatures very close to absolute zero. The theory was later confirmed experimentally. At this stage he returned to the United Kingdom where he spent some time as a lecturer at the University of Birmingham.