Scottish brewer Innis & Gunn aims to get drinkers’ rocks off with a bottle-conditioned beer called Hot Rocks that takes inspiration from ale brewed in the Stone Age.

The brewer claims Britons have been enjoying beer for 6,000 years and it scoured records of ancient archaeological artefacts to try to recreate what our Stone Age ancestors supped.

They would not have used hops in the brewing process as hops did not appear widely in Britain until the 1500s, so Innis & Gunn has used none and focused instead on sourcing barley and botanicals ancient man might have used.

It used the historic bere barley alongside raw barley and malted barley and used sweet gale and meadowsweet for bittering and preservation, as well as horehound and pink heather – all naturally-occurring botanicals in the British Isles since 4,000 BC.

Hot Rocks owes its name to the brewing process of using hot granite rocks to caramelise the barley, extracting the malt sugars.

Merryn Dineley, an Orkney-based expert on ancient and traditional brewing, said: “I think the recipe is spot on. A proper prehistoric ale. It would actually do for an ale made in neolithic, bronze age, iron age or Viking times as well. Hot rock heating of water is fascinating, though it is quite hard to boil the water despite the hissing and sizzling of the rocks.”

Beer historian Martyn Cornell, author of Amber, Gold and Black, a history of beer styles in Britain, added: “We’ve been enjoying beer in Britain for 6,000 years, and it’s great to think we can now enjoy a beer inspired by those of 6,000 years ago. This gives a completely new meaning to the expression ‘old ale’, and I very much look forward to drinking it.”

The 7% ale is a limited-edition offering available from the Innis & Gunn website, and costs £15 for a 33cl. Just 120 bottles will be sold.

Dougal Sharp, founder and chief executive at Innis & Gunn, said: “I started Innis & Gunn in 2003 to experiment with flavour and make beers, using traditional and innovative methods, that are highly distinctive for their depth of flavour. 

“In making Hot Rocks, we’ve gone deeper than any other brewer into the back-catalogue of British brewing, taking archaeological evidence dating back 6,000 years – well before man could write – of the earliest-known ale known to have been made on the British Isles and mashing it with all our brewing experience and knowhow to create a less rough and ready, more refined brew for the modern day, with an abv to match.  

“This brew is particularly close to my heart because I have scuba-dived a lot around the inner Hebridean coast and the use of Scotland’s indigenous granite rocks seemed so right for this special brew.”