Edinburgh's Innis & Gunn has unveiled a limited-edition beer that has been six years in the making, the longest the brewer has matured any beer to date.

Headed by master brewer Dougal Gunn Sharp, Innis & Gunn originally laid its Vintage edition down to mature back in 2015. The beer spent its first 100 days in first fill American bourbon casks and was then bottled with some live yeast, allowing the brew to slowly mature and develop in Innis & Gunn’s bonded warehouse over the last six years.

Priced at £25 per 500ml bottle, just 1,000 bottles will be available from the brewery's online shop from September 1. The 9% ABV brew is ready for drinking, or could be cellared for the future for further maturation.

HeraldScotland:

“Innis & Gunn was founded on a passion for trying different styles of maturation and Vintage achieves a special milestone for us," Mr Sharp said. "As we finally release this one-of-a-kind beer after six years, it marks our longest maturation to date and one which is almost unheard of in brewing."

The result of this uncommonly long maturation is described as "exceptional and surprising", with those who have tasted Vintage so far finding different things at different times as they sip and savour the beer. A universal observation is how the aromas and flavours of Vintage change over time after pouring into a glass.

READ MORE: Edinburgh's Innis & Gunn ‘back with a bang’

Mr Sharp added: “It starts with a champagne-like aroma, which carries into the taste, but this soon dissipates as the beer opens up to give aromas and flavours of Christmas cake, ginger and dark treacle with hints of cocoa.

"Wait five minutes more and liquorice and caramel start to emerge on the palate alongside more of the bourbon, malt and vanilla notes we are best known for. At some point it will pass through a phase of smelling just like a good white Burgundy. Towards the end of the glass, orange marmalade, toasted butter and smooth espresso.

“Vintage is a journey - both for us as a brewer and for the drinker - as it offers such a wonderful and unusual experience, with its evolving aromas and flavours, from first pour to last sip.”