The makers of Irn-Bru are to produce a limited edition of the soft drink using a recipe that dates back almost 120 years

Robin Barr, the great-grandson of the soft drinks company’s founder Robert Barr, unearthed a recipe for the popular product – known as “Scotland’s other national drink” –  from 1901.

Now a limited edition Irn-Bru 1901 is to hit the shops in Scotland from December 2 as a “premium product”, makers AG Barr announced.

The  “old and unimproved” version of the Scottish staple is being made strictly in accordance with the authentic, handwritten recipe – which has been recreated by research and development experts using modern equipment at Barr’s state-of-the-art factory in Cumbernauld.

It is claimed no-one alive will have ever tasted Irn-Bru in this original form due to the age of the recipe – which was uncovered in a handwritten book stored deep in the company’s archives.

Mr Barr said: “The 1901 recipe has aged beautifully over the last 118 years.

“For a limited time, we’ll be producing a premium ‘old and unimproved’ Irn-Bru 1901 just as it was enjoyed by our first fans.

“This is Irn-Bru as you’ve never tasted it. It’s a chance to enjoy a unique and authentic piece of Scottish history – but don’t hang about, we don’t think it will be around for long.”

While the secret flavour essence in Irn-Bru 1901 is  unchanged from the one that is used today, this version of the drink does not contain any caffeine, with the product sweetened by sugar.

It will be sold in glass 750ml bottles and branded with the classic strongman logo, harking back to the company’s early days.

Fans of the fizzy drink will be able to buy the old-style Irn-Bru in Scottish shops from December 2, with a bottle expected to cost about £2.