Professor Stephen Hawking, the world-renowned physicist and cosmologist who has motor neuron disease, has been taken to hospital by ambulance after falling “very ill”, the University of Cambridge announced.

The scientist, 67, who is the university’s Lucasian Professor of Mathematics, was admitted to Addenbrooke’s Hospital for tests at lunchtime after a chest infection he has had for two weeks worsened.

“Professor Hawking is very ill,” a spokesman for Cambridge University said. “He is undergoing tests. He has been unwell for a couple of weeks.” The spokesman described the scientist’s condition as “comfortable”, but confirmed that he would stay in hospital overnight. An update on his condition is expected today.

Professor Hawking fell ill two weeks ago while on a speaking tour of the United States, and he cancelled a keynote lecture to a conference on the origins of life at Arizona State University. His condition has not improved since he returned home.

Professor Peter Haynes, Head of the University’s Department of Applied Mathematics and Theoretical Physics, said: “Professor Hawking is a remarkable colleague, we all hope he will be amongst us again soon”.

The scientist is almost completely paralysed by the effects of amyotrophic lateral sclerosis, a serious form of motor neuron disease that causes progressive degeneration of the nerves that control muscles. He was initially expected to live only for another one or two years when the condition was first diagnosed in 1963, when he was 21.

Only about five per cent of people with ALS survive for more than 10 years, yet Professor Hawking has lived with the condition for more than four decades.

Since 1985, when he contracted pneumonia and had to be given a trachaeotomy, he has spoken using a voice synthesiser, which he operates using cheek muscles over which he still has control.

Professor Hawking, whose 1988 book, A Brief History of Time, spent a record 237 weeks on the Sunday Times bestseller list, is one of the world’s leading cosmologists and theoretical physicists.

His popular writing about physics and cosmology is widely thought to have transformed science publishing, and his instantly recognisable voice and appearance have led to many appearances as himself in television shows, including The Simpsons, Star Trek: The Next Generation and Red Dwarf.

It was announced last year that he will step down as Lucasian Professor in the summer, at the end of the academic year. It is Cambridge University policy for holders of the title, who have in the past included Sir Isaac Newton, to retire at 67. Professor Hawking has said he intends to continue working as an Emeritus Professor.

His scientific achievements include his 1974 calculation that black holes should produce subatomic particles, a phenomenon now known as Hawking radiation that is widely accepted by physicists.

Definitive evidence for his proposals may be found by the Large Hadron Collider (LHC), the £4bn atom-smasher that will restart at the CERN particle physics laboratory in the autumn. Should the LHC find such evidence, Professor Hawking would become a strong contender for the Nobel Prize.

Professor Hawking has a history of putting money on his scientific beliefs. He has bet Gordon Kane, a physicist at the University of Michigan, £50 that the Higgs boson that is proposed to give matter its mass, will not be found — a wager that has infuriated Professor Peter Higgs, who proposed the particle. In 2004, he conceded a bet he had made with John Preskill, of the California Institute of Technology, after finding evidence that suggested that black holes to do not destroy everything that is sucked into them.

Professor Hawking has three children by his first wife, Jane, from whom he separated in 1991. He was divorced from his second wife, Elaine, his former nurse, in 2006.

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