Cut the pork fillet into 4 pieces — each will be about 6 cm (2 1/2 in) long. Stand each piece on end and flatten with the hand until it is 5 cm /2 in wide and 25 mm (1 in) thick. Wrap a slice of bacon around each steak and tie in place with fine string. Season on both sides with freshly ground black pepper and allow to come to room temperature.

Heat the grill without the grid to high. Season the pork tournedos on both sides with salt and more freshly ground black pepper, and brush with olive oil.

Brush the grill grid with oil and place the pork tournedos on the grid. Grill, with the grid 7.5 cm (3 in) from the heat, for 10 minutes, turning after 7 minutes and brushing again with olive oil.

Place the mushrooms on the grid with the tournedos and brush them with olive oil, then grill for a further 5 minutes, brushing the mushrooms with oil occasionally.

Remove the strings from the steaks, leaving the bacon in place surrounding the tournedos like a collar. Arrange the steaks on a heated serving platter. Garnish with the mushrooms and watercress and serve.