Willard S Folsom knew a thing or two about collecting whisky. The San Francisco-based collector devoted 18 years of his life to amassing a unique collection of more than 3,000 bottles, which included rare single malts from now-closed distilleries such as Ben Wyvis.

Part of the collection built by Folsom, who died last year, goes under the hammer at Bonhams, the auctioneers, next month in what is thought to be the largest single-owner collection ever to go on sale.