Preheat the oven to 180C Fan/Gas 7. Lightly grease one baking tray.
Put the flour, baking powder, cranberries and sugar in a large bowl. Add the butter and rub in with your fingertips until the mixture resembles fine breadcrumbs.
Crack the egg into a measuring jug, then add enough milk to make the total liquid 125ml. Stir the egg and milk and then gradually add to the flour mixture until you can form a soft, sticky dough. You will not need to use all the egg and milk mixture.
Turn out onto a lightly floured work surface, knead lightly before rolling out to 2cm thick.
Cut into as many rounds as possible with a fluted 5cm cutter or a glass and place them on the prepared baking trays. Brush the tops of the scones with the extra milk and egg mixture.
Bake for 15 minutes, on the lower shelf in the oven, until the scones have risen well and a pale, golden-brown colour. Let them cool before devouring. Whilst the scones are baking prepare your jam.