We washed the blackberries well, poured the gin out of a bottle into a jug, then added about half a bottles worth of berries. It is worth weighing this as you go because we then put in the same weight of sugar into the bottle and then added the gin back in. And due to the laws of physics there was obviously some displaced gin that would not fit back in the bottle so we're in for a few gin and tonics tonight. Yippee!
In a about three months time, when the fruit is looking all bleached out and ghostly the berries need to be strained out. Then the gin is left another month or two to steep and then it will be ready - just in time for Christmas.