1. Thread the prepared grapefruit, courgettes, mushrooms and tomatoes on to skewers and lightly brush with oil. Place under a grill and cook under a medium heat for 8 minutes, turning frequently. 2. Mix together in a bowl the fromage frais, mayonnaise, Worcestershire sauce, tomato pur?e, garlic and juice from half the grapefruit. Season to taste. 3. Segment the remaining half grapefruit, roughly chop it and add to the sauce. 4. Serve the kebabs on a bed of rice accompanied by the sauce.