Say ‘Scottish alcohol’ to someone and they’re pretty likely to think of whisky. Most Scottish whisky is aged in American Oak barrels that were previously used for Bourbon. According to American regulations they can only be used once for Bourbon so these are available relatively cheaply (they are not cheap to make and the UK could not support demand for new barrels by itself). The barrels, and their previous usage, lends the whisky specific flavours and colouring. Prior to this sherry, port and madeira barrels came into British ports, and these were re-used for whisky. The European Oak and the sweet wines within influenced the whisky’s colour and taste.
While a lot of whisky nowadays is lighter in colour and taste drier (due to the more economic use of bourbon barrels) some distilleries still use sherry casks from Spain, specifically Oloroso Sherry from the South West of Spain. This actually uses American oak in its ageing process, and as a result of being used to age sherry it gives whisky a nutty taste, with fruits such as fig and spiced orange in the mix as well. The whisky is oilier and takes on a darker hue, often a deep red mixed in with the amber.
While this sort of whisky is less easy to find in supermarkets than the Bourbon-barrel aged types, it’s still common enough to find in specialist shops, starting at around the £30-£35 mark for Glenfarclas 10 year old (which is the sherry-aged whisky most commonly found in supermarkets). Sampling such whisky is akin to stepping back in time to the Victorian era, albeit without the Grandfather paradox/diptheria type problems, as this is how whisky tasted in those days. It helped keep the Scottish whisky industry going and for that we have Spain to be thankful for.