For the roast beef
- 225g piece fillet of beef
 - ¬? tsp mustard powder
 - 1 tbsp olive oil
 
For the Yorkshire puddings
- 2 tbsp sunflower oil
 - 100g plain flour, sifted
 - 2 eggs
 - 175ml milk
 
For the horseradish cream
- 1/2 tsp English mustard
 - 1 tbsp grated fresh horseradish
 - 1 tsp sugar
 - 1 lemon
 - 75ml double cream
 - sea salt and freshly ground black pepper
 - fresh watercress sprigs, to garnish