Flavoured grapefruit juice
Peel thin strips of zest from the grapefruit using a peeler, press out the juice. Heat the grapefruit juice and zest in a small pan with the bay leaf and cinnamon, cover and allow to infuse for approx. 30 mins. Pour the flavoured grapefruit juice through a fine sieve into the glasses.
Gin and tonic
Add gin and ice cubes to the grapefruit juice in the glasses and top up with tonic. Decorate each glass with one wedge of grapefruit, 1 bay leaf and 1/2 a cinnamon stick, serve immediately.