Put the cherries in a sieve, rinse with cold water then drain and pat dry with kitchen paper. (This ensures they don't sink during cooking.) Halve 50 g (2 oz) and reserve for decoration. Roughly chop the remainder.
Beat the butter and sugar together in a mixing bowl or a food processor until pale and creamy. Stir in the orange rind then gradually mix in alternate spoonfuls of beaten egg and flour until all has been added and the mixture is smooth.
Fold in the chopped glacé cherries and cranberries. Spoon the mixture into an 18 cm (7 inch) deep round cake tin lined base and sides with nonstick baking paper. Spread the surface level then lightly press the reserved halved cherries into the cake mixture and sprinkle with the crushed sugar lumps.
Bake in a preheated oven, 160°C (325°F), Gas Mark 3, for about 1 hour 10 minutes–1 hour 20 minutes until well risen, the top is golden brown and a skewer inserted into the centre comes out clean.
Leave to cool in the tin for 10 minutes then loosen the edges, turn out on to a wire rack and peel off the lining paper. Leave to cool completely. Store in an airtight tin for up to 5 days.