Mix all the ingredients together in the slow cooker pot.
400 g tin red kidney beans, 300 g tin chickpeas, 400 g tin borlotti beans, 400 g tin chopped tomatoes, 4 tbsp tomato purée, 200 ml hot water, 1 tsp vegetable bouillon powder, 1½ teaspoons heaped of chipotle chilli and smoked paprika paste, 1 red onion, 2 sticks of celery, salt and pepper, 1 tsp dried sage