 Using distillate obtained from Jameson's nearby Bow Street Distillery, Mitchell & Son matured whiskey in a mix of casks that had been used to hold both dark and light sherries in their cellars under Fitzwilliam Lane in Dublin.For the first five years of maturation, half of the whiskey was aged in casks that had previously held Oloroso and other darker sherries, with the other half aged in casks that had held lighter finos.This combination prevented the darker wines from overpowering the whiskey.