200 g (7oz) unsalted butter, softened, plus extra to grease
200 g (7oz) caster sugar
4 medium eggs, beaten
200 g (7oz) self-raising flour
1/2 tsp baking powder
finely grated zest 1 lime
75 ml (3 fl oz) gin
For the Syrup and Topping
25 g (4oz) caster sugar, plus extra to sprinkle
125 ml (4 fl oz) tonic water
31/2 tbsp gin
2 limes, cut in half through their length and sliced into 3mm (1/8in) half moons
100 g (3 ½oz) icing sugar, sifted
Preheat oven to 180°C (160°C fan) mark 4. Grease and line base and sides of a 900g (2lb) loaf tin with baking parchment. In a large bowl beat butter and sugar with a handheld electric whisk until light and fluffy – about 5min. Gradually add eggs, beating well after each addition.
Fold in flour, baking powder and lime zest, followed by the gin. Spoon into prepared tin and bake for 55min-1hr or until a skewer inserted into the centre comes out clean.
Meanwhile, make sugar syrup: gently heat the caster sugar and tonic water in a small pan, stirring often, until the sugar dissolves. Turn up heat and boil for 1min. Spoon 2tbsp of the syrup into a small bowl and mix in 2tbsp of the gin (this mixture will be used to soak the loaf later). Set pan of remaining syrup aside.
As soon as the loaf comes out of the oven, poke holes into the top with a skewer and drizzle over the reserved syrup/gin mixture. Cool loaf in tin on a wire rack.
Meanwhile, make the candied lime slices. Reheat the remaining sugar syrup in its pan until boiling, then add the lime slices. Simmer for 10-12min until the slices are translucent. Lift out slices with a slotted spoon on to baking parchment, then sprinkle both sides of the lime slices liberally with caster sugar. Leave to dry.
Make icing by mixing together icing sugar with remaining 1½tbsp gin. Remove cooled loaf from tin, transfer to a board and peel off parchment. Pour over icing and decorate with the dried candied lime slices. Leave the cake to set before serving.