Set the oven at 200C/gas mark 6. Place a large piece of tin foil in a roasting tin. Wash and trim the beetroot, taking care not to break their skins, and place them in the foil.
Add the olive oil, two tablespoons of water and a grinding of salt and pepper, then scrunch the edges of the foil together to seal. Bake the beetroots for 45 minutes to an hour till tender to the point of a knife, then remove and set aside.
Slice the radishes in half and put them in a mixing bowl. Slice the peel from the orange flesh, taking care to keep any escaping juice, remove the segments from the membranes, then add the segments to the radishes.
Peel the beetroot and cut each one in half, then into quarters, and add them to the mixing bowl.
Wash and trim the watercress. (if wished you can dunk it in a bowl of iced water for 20 minutes to crisp it up.) Put the mint and parsley leaves in with the orange and beetroot together with the trimmed watercress and the pumpkin seeds.
Make the dressing: put the blood-orange juice in a small bowl, add the sherry vinegar, season with salt and pepper then pour over the salad and toss gently.