Combine digestive biscuits and sugar in a 9 inch pie pan. Add butter and mix till moist. Press mixture evenly over sides and bottom of pan to form the crust. Refrigerate for at least 30 minutes.
A store-bought graham cracker crust is also sufficient and quite tasty.
Blend cream cheese and condensed milk together till smooth and creamy. Add lemon juice and vanilla and mix till combined. Pour into crust. Refrigerate for at least 2 hours before serving, or until the filling is firm.