Wash the plums then pierce all over with a fork
Put into a sterilised Kilner jar / jars with the sugar then pour the gin over
Seal the jar and shake it
Leave the jar in a cool dark cupboard, shaking again every day for the next 3 days to dissolve the sugar well
Let stand for 3 months without disturbing it, then strain through a fine muslin cloth
Don't discard the plums. They're perfect for a fruit crumble with their extra flavouring now!
Pour the gin into a clean, sterilised bottle / bottles and enjoy!