The 900th Birthday Brew is being produced at the estate's famous 18th century brewery to mark the anniversary of the signing of the Royal Charter by Alexander I at the house in 1107.

It will join the world-renowned Jacobite and House ales, as well as a range of other special edition beers such as the 1000th Brew, the Silver Wedding Brew and Catherine's 21st, all brewed at Traquair.

Only 40,000 bottles of the limited edition beer will be produced, of which a quarter will be exported. The rest are available from both the Traquair House shop and independent retailers.

Catherine Maxwell Stuart, the 21st lady of Traquair, took over the running of the family home and brewery in 1990.

She said: "It's very important to mark the anniversary.

"Not very many houses can claim to have been around for 900 years, particularly lived-in houses. It's remarkable that it's survived all these years, especially through Jacobite times.

"The new beer's been about a year in the planning. We obviously knew the 900th birthday was coming up and we wanted to mark it appropriately. The brewery is very important to the life of the house, so it was an obvious way to mark the occasion."

Traquair House has become renowned for producing world-class beers since 1964, when Peter Maxwell, the 20th Laird of Traquair, began brewing in the ancient brewery. In 2005, it was voted 20th best brewery in the world by a popular consumer website which also currently lists Traquair Jacobite Ale as the best beer brewed in Scotland.

The 900th Birthday Brew is packaged in a specially designed silk-screened bottle and has an ABV of 9 per cent.

"It's pretty strong, so you really need to be sitting down at the end of the day to enjoy it," Ms Maxwell Stuart joked.

A series of events at Traquair House throughout the year will also celebrate the estate's 900th anniversary. The annual Easter Eggstravaganza in April will this year include 900 special golden bunnies hidden in the grounds and the Medieval Fayre in May and the Traquair Fair in August are also expected to draw the crowds.

However, at the heart of festivities will be the 900th Birthday Celebration Weekend from June 29-July 1, which will include a series of talks and discussions by well known authors and writers, including David Starkey and William McIlvanney, as well as children's events on Sunday.