Speaking at the G8 Innovation Conference in London, the prime minister said the "grand challenge" would be like the Britain's Got Talent of the science world, with leading scientists coming together to debate what the greatest challenge facing the world is today, before opening it up to the public. 

"Two hundred and ninety-nine years ago the British government decided to establish the longitudinal prize to the public. It's time to do that again," he said.

Although the current government won't go as far as his 1714 predecessor and make the prize an act of Parliament, it will be broad in scope. The UK's best researchers, across multiple fields, will have the chance to decide what is the most pressing challenge in need of an innovative jump forward, with the public having a hand in deciding that agenda.