Seal the sirloin all over including the ends. Set aside in the roasting tin. Preheat the oven to 220C/200C Fan/Gas 7. Meanwhile mix together the mustard, salt and pepper and rub all over the sirloin.

"Ask for a triangular-shaped cut from the top part of the sirloin with a thick, untrimmed fat cap on one side ... You can roast it in the oven, pan-fry it quickly, or toss it on the grill.