For 250 years women have been forced to ponder what exactly takes place at the secret candlelight meetings held by the Speculative Society.

Now one of the last bastions of male privilege, which operates within Edinburgh University, has been ordered to open its doors to female members – or face eviction.

A debating and literary society, whose members have included Robert Louis Stevenson and Sir Walter Scott, the all-male Speculative Society has held its meetings in the grand rooms of the University’s Old College since 1764.

But the mysterious “Spec” has been told to throw its doors open to the wider public and admit female members after the club’s operation was criticised in a review carried out by Professor Mary Bownes, Edinburgh's vice-principal.

Concerns were raised over the club’s relationship with the university – which owns the society’s base – after it emerged it was occupying college premises rent-free.

One of the world’s oldest clubs, the society has been given six months to overhaul its membership rules or face being kicked off the premises.

The Society is one of the last male-only institutions in Scotland, following the September vote by the Royal and Ancient Golf Club of St Andrews to admit women, over-turning a 260-year ban.

The Speculative Society’s membership is thought to include leading Scottish lawyers and academics. Operating within three history rooms in the Old College, the club is not officially part of Edinburgh University but has maintained rent-free privileges.

The debating and literary society's members have included Robert Louis Stevenson and Sir Walter Scott (Getty Images)

Members say the purpose of the society’s candelight meetings is to advance public speaking and literary composition. Although there is no official “ban” on female members in its rules, no woman has ever been invited to join the “Spec”.

A university spokesman said: “The university is committed to the ethos of equality and diversity on its campus.

“In light of this, Professor Bownes was asked to carry out a review of the historic links between the university and the Speculative Society, which occupies rooms in Old College.

“Her report, which has been agreed by senior management, proposes that the Speculative Society is given six months to show that it is changing to comply with this ethos by admitting female members along with males. The report also recommends that the society agrees to make the historic rooms more accessible to the public.”

Allan Massie, a journalist and honorary member of the society, said it was “about time” the club introduced female members.

Peter de Vink, a Midlothian East councillor and long-time member, said the society must adapt or die. He told Edinburgh Evening News: “If they think in this day and age you can avoid having lady members, they can’t be of this world.

“They are really woefully short of members, and if they brought in female members it would boost the membership.

“The society is 250 years old and it’s going to be destroyed by a handful of people if they’re not careful. As I understand it, it’s only a handful of very outspoken people who are stopping the inevitable.

“It’s a famous, famous society with a long history. It’s got a fantastic membership, and to let that all get smashed is so irresponsible.”