Step 1

For the roast beef, heat the oil in a roasting tin on the hob. Seal the sirloin all over including the ends. Set aside in the roasting tin.

Step 2

Preheat the oven to 220C/200C Fan/Gas Meanwhile mix together the mustard, salt and pepper and rub all over the sirloin. Pour a little water into the roasting tray (just enough to cover the bottom).

Step 3

Place the beef in the oven for 30 minutes. Then reduce the temperature to 160C/140C Fan/Gas 3 and continue to roast for a further 20–40 minutes, depending on how rare you like your beef. (For rare, roast for 20 minutes per kilo or 9 minutes per lb; for medium, 30 minutes per kilo or 14 minutes per lb; for well-done, 40 minutes per kilo or 18 minutes per lb.)

Step 4

To test that the beef is ready, use a meat thermometer – see the Recipe Tips for temperature guidance. Remove the joint from the oven and set aside to rest for 15 minutes.

Step 5

To make the creamed horseradish, mix all the ingredients together to a smooth consistency. Season with salt and pepper.

Step 6

Carve the beef and serve with the horseradish on the side.