Mick Jagger. Photo: Eric Thayer/Reuters

Singer Mick Jagger, actress Judi Dench and scientist Stephen Hawking are among 200 British stars who have signed a letter urging Scotland to remain part of the UK, six weeks before a historic referendum on independence.

The letter, an attempt to sway Scots before the September 18 vote, was organised by Let’s Stay Together, a group which says it aims to give a voice to the millions of Britons outside Scotland who don’t have the right to vote.

Opinion polls show most Scots will vote against breaking the 307-year union with England. But they also show that many have not yet decided how they will vote, injecting some uncertainty into the outcome.

The letter, signed by a Who’s Who of celebrities, many of them English, was organised by Dan Snow and Tom Holland, well-known TV historians in Britain.

Released at an event on the banks of the River Thames in London close to Tower Bridge, organisers said an extraordinary list of famous Britons had signed the letter, reflecting the fact that non-Scots were not indifferent to Scotland’s fate.

“The decision on whether to leave our shared country is, of course, absolutely yours alone,” said the letter, which was ad-dressed to ‘Dear voters of Scotland’.

“Nevertheless, that decision will have a huge effect on all of us in the rest of the UK. We want to let you know how very much we value our bonds of citizenship with you, and to express our hope that you will vote to renew them.”

Other big names who signed the appeal include actress Helena Bonham-Carter, composer Andrew Lloyd Webber, singer Cliff Richard, show business impresario Simon Cowell, and actor Dominic West.

Between them, organisers said the signatories had 18 Olympic gold medals, 44 Bafta awards, one Nobel prize and two Turner prizes.

Other celebrities, notably singer David Bowie and Harry Potter author J.K. Rowling, had already spoken out against independence, but not in such numbers and at the same time.

The pro-independence camp has its own celebrity backers including James Bond actor Sean Connery, actor Brian Cox and novelist Irvine Welsh.