Preheat the oven to 180°C/ Fan 160°C/Gas 4 and line a large baking tray with baking paper. Put the flour, baking powder, sugar and salt into a large bowl.
Add the butter and rub it into the flour using your thumbs and fingertips, trying not to get it on the palms of your hands. (If the mixture gets too warm, it will become tough, so the idea is to use the coolest parts of your hands to do this.)
When the mixture resembles breadcrumbs, add the egg and buttermilk, then gather into a ball and turn out onto a floured work surface.
Knead the dough quickly and gently, then pat the dough out to 2½ cm thick and cut into circles with a cookie cutter about 5cm wide (or use a glass if you don’t have a cutter).
Transfer the scones to the baking tray, brush the tops with milk, then bake for 10–15 minutes until well-risen and light golden. Leave to cool slightly, before serving warm with butter or cream and jam – and a good strong cup of tea.