Tip the blackberries and sugar into a 1.5-litre sterilised jar. Pour over the gin, seal the jar and swirl around to dissolve the sugar. Store in a cool, dark place and turn the jar once a day for the first week.

After two-three weeks, strain the gin through a sieve. Pour the gin into bottles, and label. The gin will keep its colour for a few months and will be drinkable for up to a year. Use the infused blackberries in a cocktail like a bramble, or in a trifle.