2 celery sticks, thinly sliced
1 tbsp chopped fresh parsley
2 spring onions, finely chopped
1 tbsp chopped fresh tarragon
1 large tomato, deseeded and finely diced
2 tsp Dijon mustard
1 x 400g tin mixed bean salad, drained and rinsed
salt and freshly ground black pepper
3 tbsp olive oil
1 tsp sugar
1 tbsp white wine vinegar