Old Particular Secret Grain 20-year-old is a single grain whisky bottled at natural cask strength. Its age and Pedro Ximenez cask influence suggest a style that can be richer and sweeter than many lighter grain whiskies.
For a novice drinker, expect a smooth grain-led base with added depth from cask maturation, likely bringing darker sweetness and oak alongside the higher strength. A small splash of water may help open it up.