Line a 20cm springform cake tin with baking parchment. Combine the digestives and butter in a bowl and mix well. Press into the base of the prepared cake tin.
Combine the mandarin oranges and sugar in a food processor (reserving a few segments for decoration). Transfer the purée to a clean pan. Soak the gelatine leaves in cold water for 5 to 6 minutes. Squeeze out any excess liquid then add to the orange purée and warm over a low heat until dissolved.
In a large mixing bowl, whisk the double cream until light and fluffy, then mix in the cream and cream cheese. Gradually add the mandarin purée mixture and whisk until light and airy. Spoon into the prepared cake tin and smooth over the biscuit base. Chill in the fridge for 6 hours or overnight.
Remove the cheesecake from the fridge and carefully pop out of the cake tin and place onto a serving plate. Arrange the reserved mandarin segments on top of the cheesecake and slice and serve.