Put the plums in a shallow pan with the sugar, butter and damson or sloe gin. Allow to warm slowly over a low to moderate heat for 5 minutes or so until the juices start to run.
Tip the fruit and its juice into a deep pie dish.
Rub the butter into the flour with your fingertips. When the mixture resembles coarse fresh breadcrumbs stir in the ground almonds and sugar. Sprinkle a tbsp or two of water over the mixture and shake the bowl so that some of the crumbs stick together in small lumps.
Scatter the crumble over the fruit then bake for about 35 minutes. The crumble is done when the crust is pale gold and marked here and there with juices.