Heat a non-stick frying pan over medium heat. Skip this step if using tinned tuna
Spray the fish with the olive oil spray, place in the frying pan and cook for 3-4 minutes on each side or until just cooked. Set aside. If using using tinned tuna then you can skip this step
Combine the beans, tomatoes, cucumber, olives, onion and basil in a bowl.
Mix together the olive oil, vinegar and mustard and pour over the vegetables, tossing well to combine.
Cut the fish into large chunks and combine with the salad.
Serve on a bed of green salad leaves with freshly ground black pepper