For the base - Line the base of a 20cm spring-form tin, at least 7cm deep, with baking paper and set aside.
Blitz the digestives in a food processor the drizzle in the melted butter and blitz until a crumb forms. Tip the mixture into the prepared tin and press down with the bottom of a glass until you have an even layer. Refrigerate for at least 30 minutes.
For the filling - Cover the gelatine leaves with cold water and leave to soak for 5 minutes.
Beat the cream cheese, mascarpone and icing sugar together until smooth. Add the orange and lemon zests and cream and beat again until slightly thickened but still pourable. Put the boiling water into a small bowl and add the soaked gelatine. Stir until it has dissolved and there are no lumps. Add to the cheesecake mix and beat a final time. Pour onto the base and carefully smooth with a palette knife. Return to the fridge while you make the jelly.
For the Pimm's Jelly - Cover the gelatine leaves with cold water and leave to soak for 5 minutes.
Bring the sugar and water to the boil. Once boiling, add the lemon juice and peel, remove from the heat and pour the contents of the pan into a bowl and place into the fridge until cold. Once chilled, remove the lemon peel and add the Pimm’s and gin. Pour ¼ of the Pimm’s mixture into a pan and reheat gently over a low-medium heat. Dissolve the soaked gelatine sheets in the liquid and once dissolved, pour back into the bowl containing the rest of the chilled Pimm's mixture and finally add the citric acid. Arrange the sliced strawberries and a few mint leaves over the top of the cheesecake in a circular pattern, then carefully pour ½ of the jelly over the cheesecake and leave to set for 2 hours.
Remove the cheesecake from the fridge and pour over the remaining jelly then leave to set to a further 2 hours or until the jelly is completely set. You must pour the jelly in 2 layers or you risk ruining the strawberry pattern you’ve just made!
When ready to set, use a blow torch to heat the outside of the cake tin, then remove the tin and transfer the cheesecake to a serving plate. Use a large knife dipped in hot water to slice the cheesecake neatly.