I wanted a 25mm hole for an outside tap (allowed for a bit of insulation stuffed in before making good. Pilot drill from inside, no plaster so went centre brick. Through inner leaf horizontally, hit the bottom edge of a brick on the outer leaf. Ran the 25mm drill through from each side to cavity and 15mm pipe wouldn't go through. No debri - just the f'ing courses out and enough offset for a c*ck-up. Took far longer to 'fettle' the hole than it did to drill it.