Heat the oven to 220C/fan 200C/gas 7. Butter a large baking sheet. In a large bowl, mix together the flour, baking powder and salt. Rub in the butter with the oil, until the mixture resembles fine crumbs, then add the tomatoes, cheese and olives. Make a well in the centre, pour in the milk and mix with a knife, using a cutting movement, until it becomes a soft ‘stickyish’ dough. (Use all the milk – it helps give a light texture.) Don’t overhandle the dough.
Flour your hands and the work surface well, and shape the dough into a round, about 3-4cm thick. Cut into eight wedges and place them well apart on the baking sheet. Brush with beaten egg and bake for 15-20 mins until risen, golden and springy to the touch. Transfer to a wire rack and cover with a clean tea towel to keep them soft. These are best served warm and buttered. Will keep for 2-3 days in an airtight container.