Blitz the ginger nut biscuits to a crunchy crumb consistency either in a food processor or place in a bag and bash with a rolling pin.
Melt the butter in a medium sized saucepan, then stir in the crushed biscuits.
Press the biscuits into the bottom of the greased cake tin, ensuring all of the bottom is covered evenly, then place into the fridge for a minimum of 20 minutes.
In a bowl whisk the condensed milk to slightly soften it and then gradually whisk in the lemon juice and zest. Then fold in the cream cheese.
In a separate bowl whip the cream by hand or use a stand mixer until it just begins to go stiff. Then fold the cream into the lemon mixture and pour the whole mixture over the biscuit base. Smooth over with a palette knife.
Place the cheesecake into the fridge to chill for 4 to 6 hours. If you can make this the day before and chill overnight, then even better.
Before serving, remove from fridge for 20 minutes or so to allow the cheesecake to return to room temperature, remove from the tin and decorate with thin slices of lemon.
This cheesecake is possible to freeze. Cut it into individual portions first prior to freezing.