Prepare your barbecue for the steak by banking the white hot coals on one side of the grill (or, if you’re using gas, turning off two burners). Grill the sirloin for 15-20 minutes over the hot coals, turning to sear it evenly on all sides, and moving it away from the coals onto the indirect heat when flames flare up because of the dripping fat. If you have a kettle barbecue, you can put the steak over the indirect heat and close the lid. If you’ve got an open grill, keep moving the steak over the grill to make sure it’s evenly cooked on all sides. Use
a thermometer to check the core temperature and when it’s at 50 degrees, season it and rest it for 15-20 minutes. Alternatively, sear in a grill pan for 10 minutes until charred all over, then transfer to an oven at 220C/200C/gas 7 for 30 minutes until the middle reaches 50C.