Zest the oranges into a large, sealable jar (I use a 1 litre Kilner jar I got on Amazon). Juice one of the oranges into jar, peel the other two and take out the segments.
Put the sugar and about 100 ml of the gin into the jar. Seal it and shake it until the sugar dissolves. Add the orange segments and the remaining gin to the jar, shaking gently to mix.
Leave it in a cool, dark place for a fortnight (or longer, if you can resist) until it is opaque and yellow; remembering to shake it every day or so. Decant through muslin (or a sieve lined with kitchen roll, it does the same job) and pour the gin into a sterilised bottle. It will keep for up to three months – allegedly – although none of mine have every seen passed a few weeks.
As I don’t like to see good food going to waste I used the orange flesh and zest that was left to add extra flavour to my Seville orange and gin marmalade.
Obviously responsible drinking is encouraged, but there’s not a lot that can be done about it if you decide to ‘forget’ this.