The day before serving, make the jelly by bringing 1 litre of water to the boil with the sugar, lime zest and juice. Soak the leaves of gelatine in a bowl of ice-cold water. When the sugar has dissolved, remove the pan from the heat. Squeeze the excess water from the gelatine, then add to the pan. Pass the syrup through a sieve into a bowl, then allow to cool to room temperature.
Ladle a layer of jelly into six ramekins or little jelly moulds, scatter in a layer of raspberries, then leave in the fridge for 1 hr or so to set. Top up with a bit more of the jelly, then leave to set. Continue with a layer of strawberries and then blueberries, remembering to set each layer before the next is started. Once the moulds are full of fruit, top with a drizzle more jelly, then place in the fridge. Leave overnight to set.
To serve the jellies, briefly dip the moulds in hot water, then loosen from the sides and turn out onto small plates. Serve with clotted cream and shortbread.