Tip the blackberries into a large sterilised mason jar and gently muddle them with the end of a rolling pin.

Add the sugar and whisky, seal the jar and give it a good shake. Store in a cool, dark place (give it a good shake every other day to help the sugar dissolve) for at least three weeks (it will get better the longer you leave it), tasting regularly until you’re happy with the flavour. Once the whisky is ready, filter out the berries through a piece of muslin or jelly bag (or keep them in for bursts of juicy fruit while you drink) and seal in a large sterilised bottle.