ooo--can you post a link to the recipe? 
No link, as it was just passed down from a relative many years ago -- hence the imperial measurements. It's an easy-peasy no bake recipe:
Gwyn's Lemon Cream Pie
6 oz ginger nuts
3 oz butter, softened
2 large lemons
7 1/2 oz double cream
1 7-oz tin sweetened condensed milk
(1) Crush the ginger nuts finely (in a food processor, or by wacking with a rolling pin). Combine with the softened butter and press into the bottom and up the sides of a tart pan. Chill to set.
(2) Whip the double cream until stiff. Set aside.
(3) Grate the zest from the two lemons. Squeeze the juice of the two lemons. Set aside.
(4) Fold together the condensed milk (nearly the full tin), whipped cream, lemon zest and lemon juice.
(5) Pour into the ginger crust.
(6) Refrigerate at least 1 hour. (Can be frozen a day or so ahead of use. I actually like it better slightly frozen.)
(7) Decorate with chopped crystallised ginger (or whipped cream or lemon twists) as desired before serving.