His mind has grappled with space and time, and explored the strange beauty of black holes aglow, but in recent days a more earthly problem has occupied the world's most famous scientist.

Stephen Hawking, the former Lucasian professor of mathematics at Cambridge University, must ponder how to spend $3m (£1.8m) that has landed in his bank account after winning the most lucrative science prize ever established.

The renowned physicist who missed his 70th birthday celebrations through illness in January, has won the Special Fundamental Physics Prize for a lifetime of achievements, including the discovery that black holes emit radiation, and his deep contributions to quantum gravity and aspects of the early universe.

In an email to the Guardian, Professor Hawking said he was "delighted and honoured" to receive the prize. "No one undertakes research in physics with the intention of winning a prize. Nevertheless prizes like these play an important role in giving public recognition for achievement in physics," he wrote.

The physicist, who rose to fame with his 1988 book, A Brief History of Time, and made guest appearances on The Simpsons and Star Trek, has not settled on how to spend the windfall. "I will help my daughter with her autistic son, and maybe buy a holiday home, not that I take many holidays because I enjoy my work in theoretical physics," he wrote.