Wash and trim the watercress, removing and discarding the tough stems and old leaves. Drain, dry and wrap in a clean, damp kitchen towel. Place in the refrigerator for at least 1 hour to chill and crisp.

Peel, quarter and core the pears. Cut each quarter into 3 lengthwise slices and place in a bowl with the juice of 1 lemon. Toss carefully and thoroughly to keep the flesh from turning brown.

Squeeze 3 tablespoons of juice from 1 or 2 lemons into a small bowl. Add the salt and stir to dissolve. Whisk in the honey, and then the olive oil and a little pepper. Taste and adjust the seasoning.

Arrange the watercress on individual salad plates and top with the pear slices. Scatter the walnut pieces and crumbled cheese over the top. Whisk the dressing again and drizzle over the salad or pass it separately in a bowl.