World-renowned physicist, Professor John (Jack) Allen, had a huge influence on a generation of low temperature physicists and pioneered many techniques for working at low temperatures.

During his research days he designed and built a cryostat in which, in 1932, was shown the first liquid helium and superconductivity seen in Britain. It is now lodged in the museum of the Royal Institution in London.

In 1937 he also invented the O-ring - a quick and certain vacuum seal - the indium-ring cryogenic seal came later in 1947 - although he did not patent his discovery.

Professor Allen's research was most widely known for his work on liquid helium at temperatures below four degrees above the absolute zero of temperature.

In 1938 he was credited with being one of the significant co-discoverers of the extraordinary properties of superfluid helium - a liquid state, equivalent to superconductivity in metals, in which frictionless flow can take place.

In 1958 he jointly initiated a project with two other scientists, including Nobel Laureate John Bardeen, which allowed the US to conserve three million cubic feet of helium gas which would have been lost to the world, with the installation of gas separation plants.

Born in Winnipeg, Canada, Professor Allen entered the University of Manitoba - where his late father, Frank, was a physics professor - at the age of 16, graduating with a BA in physics in 1928. With no jobs locally, he assisted his father in his own field of physiological sensory reflex and the response to stimulus and fatigue in vision and hearing.

The following year he was awarded a three-year Canadian National Research Council Scholarship to study in Toronto and obtained his MSc in 1930 and a PhD in 1933, before being awarded a two-year US National Research Council Fellowship to the Californian Institute of Technology. He later travelled to the UK and obtained an appointment funded by the Royal Society at Cambridge University where he spent a decade in teaching and research.

In the autumn of 1947 Professor Allen was appointed Chair of Natural Philosophy at St Andrews University. Twice Dean of the Faculty of Science at St Andrews, he was responsible for the creation of a Faculty of Applied Science at Dundee. Until then, engineering departments in Dundee had been in a single Faculty of Science which took in St Andrews and the then Queens College, Dundee, part of St Andrewsuntil the 1960s.

A former member of the St Salvator's College Council, he was also involved in the planning of St AndrewsUniversity's new science complex at the North Haugh which opened in 1966.

He became a Fellow of the Physical Society in 1945, a Fellow of the Royal Society of Edinburgh and the American Physical Society in 1948, and Fellow of the Royal Society in 1949. He was a member and chairman of the Very Low Temperature Commission of IUPAP from 1966-69, and a member of the British National Committee for Physics.

He was also involved in the siting of a memorial to one of the great classical experiments in physics - the measurement of Newton's universal gravitational constant G on the slopes of Schiehallion, near Loch Rannoch, by the then Astronomer Royal Maskelyne in 1774. Professor Allen designed a cairn and plaque commissioned by the Royal Society which was erected at Braes of Foss, at the foot of the path up the mountain, and unveiled in 1983 by Sir Andrew Huxley.

In 1979 he was conferred with an honorary DSc degree by the University of Manitoba and awarded a similar honorary doctorate by Heriot-Watt University in 1984.

Outside university life, Professor Allen was a prominent member of the conservation pressure group, St Andrews Preservation Trust.

Professor John F.Allen, Emeritus Professor of Natural Philosophy at St Andrews University; born May 6, 1908, in Winnipeg, Canada, died April 22, 2001 in Elie, Fife.