Pineapple ice-cream tart

My favourite dessert after an afternoon of swimming with my friends.
½ Packet Marie/Tennis biscuits, crushed
80g Butter, melted
1 Packet pineapple jelly
750ml Vanilla ice-cream
390g Tin pineapple chunks
Mix butter with biscuits
Refrigerate
Strain the juice from the pineapple and make it up to 250ml with water
Bring to the boil and pour into a 2-litre jug
Add the jelly and stir until dissolved
Refrigerate, stirring occasionally, until jelly becomes thick and syrupy
Beat ice-cream gradually into the jelly mixture
Cut pineapple chunks into smaller pieces and fold into mixture
Pour into crust, seal and refrigerate until set
Decorate with crumbled biscuit/pineapple chunks