Is this the world's oldest Scotch whisky?

Whisky found behind a hidden cellar door in a Scottish castle may be the oldest in existence, according to experts.

About 40 bottles of Scotland's national drink were discovered in Blair Castle in Perthshire late last year.

Research in the castle's archives and carbon dating technology suggest the contents date back to the early 1800s.

It may even be the same whisky tasted by Queen Victoria and Prince Albert during a trip to the castle in 1844.

Now 24 of the bottles are being prepared for sale by auction in November.

Whisky Auctioneer, which is based in Perth, said the whisky was believed to have been distilled in 1833 and bottled in 1841, before being rebottled in 1932.

After being discovered at the back of a shelf, they were sampled by family and a local whisky expert.

Since then, research has been carried out in the archives of Blair Castle and Atholl Estates, which include cellar inventories known as "bin books".

It unearthed extensive references to the production of whisky and aqua vitae, especially in the early 19th Century.

And it found that whisky was consumed during Queen Victoria and Prince Albert's three-week stay at Blair Castle in 1844.

Angus MacRaild, an old and rare whisky specialist and co-founder of Kythe Distillery, said it had been a great privilege to taste the whisky.

"This is a profoundly historic whisky and a remarkable artefact of Scottish distilling that is unlikely to ever be equalled in terms of provenance and preservation," he said.

"That it has been carefully re-bottled and preserved at natural strength, maintaining the freshness and power of this spirit for nearly two centuries is frankly, astonishing."

Carbon dating by the Scottish Universities Environmental Research Centre also supported its 19th Century origin.

Bertie Troughton, the Blair Castle resident trustee who made the discovery, said: "Blair Castle is fortunate to have one of the best archives of any historic house in Scotland and it's been wonderful to see the story of these fabulous bottles come to life in the archives.

"Whisky has always been a huge part of the history of Blair Castle and we will be building an exhibition around the bottles we keep after the auction so that all who visit Blair Castle can see it and hear the history of this incredible whisky".