IT’S old-style Irn-Bru – but not as you’ve ever tasted it.

In fact, this vintage recipe ginger set to be reintroduced to shop shelves is based on a mixture so old that it’s thought no-one currently living will have sipped it before.

Bru-wers AG Barr has dusted off its archive records to remake a recipe which dates back more than 100 years to the foundation of the firm.

READ MORE: Pat Kane: This is what our Irn Bru love affair tells us about modern Scotland

Named Irn-Bru 1901, the limited edition “old-fashioned” tipple has a frothy head and is only available in 75cl glass bottles – just like it was when it was first manufactured.

The recipe was found in a handwritten book by Robin Barr, former chair of the firm, and will be released in the run-up to Christmas.

Dubbing the “new” product “old and unimproved”, the company said: “Given the age of the recipe, it is thought that nobody in the world has tasted this early version.

The National: Robin Barr is expecting the new Bru to sell out quickRobin Barr is expecting the new Bru to sell out quick

“Irn-Bru’s research and development experts have worked to lovingly recreate the time-old recipe using modern equipment at Barr’s state-of-the-art factory in Cumbernauld to give fans across the nation a special treat.”

The release comes after the Cumbernauld-based company released a new formulation of its orange nectar, slashing the sugar content in response to a new UK Government levy on fizzy drinks.

The arrival of the sugar tax, which affects products with more than 5g of the sweet stuff per 100mls, saw Barr cut Irn-Bru’s sugar content in half to 4.7g per 100ml.

While welcomed by health campaigners, the move was not universally popular, and today remaining stocks of the now-discontinued full-sugar fizz are highly sought-after.

Retailers’ stocks are dwindling and the mark up on the original recipe of the drink is high, with online sellers offering multipacks for as much as £41 a pop. In May this year one Glasgow shopkeeper was able to sell individual cans of the drink for almost £7 each.

Sweet-toothed consumers may be pleased to know Irn-Bru 1901 does contain sugar.

However, it does not contain caffeine.

Robin Barr commented: “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.”

The first bottles will go on release on December 2 bearing labels that pay homage to the brand’s Victorian-era advertising.

The design features the famous Irn-Bru strongman and authentication from inventor Andrew Greig Barr.

However, the spelling of the name will not revert to Iron Brew in line with its original form.