British Mathematician and psychiatrist, Stephen Hawking, spent Monday night in hospital after becoming very ill at Cambridge University earlier today.

The Cambridge professor, famous for his work on black holes, is reportedly “very ill” and is undergoing tests.

The illness had caused Hawking to cancel an appearance at Arizona State University on April 6.

Hawking, 67, gained renown for his work on black holes, and has remained active despite being diagnosed at 21 with ALS, (amyotrophic lateral sclerosis), an incurable degenerative disorder also known as Lou Gehrig's disease.

He rose to wider public prominence in 1988 with the publication of his bestselling A Brief History of Time, began to develop the symptoms of incurable motor neurone disease in the 1960s, gradually losing the use of his limbs and voice.

For some years, Hawking has been almost entirely paralyzed, and he communicates through an electronic voice synthesizer activated by his fingers.

He has worked at the university's department of applied mathematics and theoretical physics for more than 30 years, but is due to step down as Lucasian professor of mathematics, a post once held by Sir Isaac Newton, at the end of the academic year.