Pre-heat the oven to 180°C, 350°F, Gas Mark 4.
Place all the ingredients in a large bowl and mix until thoroughly combined. Press into 900ml (1½ pint) ring mould or a 23 x 12.5cm (9 x 5’’) loaf tin.
Cook in the middle of the oven for 55-60 minutes, or until cooked through.
Garnish with watercress.