1) Preheat the oven to 220oC gas mark 7.
2) Pierce the potato with a fork a few times and pop in the oven for 70 minutes until crisp.
3) When ready, remove from the oven and slice in half and add butter.
4) Heat the beans and pour over the potato.
5) Mix the salad ingredients together and serve alongside the potato, drizzled with the olive oil and lemon juice.