Add the capers, olives, chopped tomatoes and vinegar, season well and simmer for 15 mins, stirring regularly until the sauce has reduced to a rich stew – the aubergines should be tender. If the aubergines are still a bit firm, continue to cook for a few minutes, adding a splash of water if the sauce thickens too much. Tip in the beans and basil, and cook for another 5 mins until the beans are hot.
