OK, finally got around to making this ... here is the recipe from Great Queen St (scribbled on a small piece of paper, so may be inaccurate):
4 lemons, peeled and squeezed
200g grated ginger
4 cloves
900-950g sugar
2 tbsp cream of tartar
5L boiling water
Boil, cool, add 2 Tbsp active dry yeast...