4 bushy sprigs dill
1 onion, small and sweet
500g/1lb small salad potatoes
2 tsp Dijon mustard
1 heaped tsp capers
6 tbsp olive oil
3 tbsp white wine vinegar
2 tbsp white wine vinegar
6 thin rashers smoked streaky bacon
2 whole smoked mackerel (or 4 fillets)