Zesty haddock with crushed potatoes & peas

INGREDIENTS

• 600g floury potatoes , unpeeled, cut into chunks
• 140g frozen peas
• 2½ tbsp extra-virgin olive oil
• juice and zest ½ lemon
• 1 tbsp capers , roughly chopped
• 2 tbsp snipped chives
• 4 haddock or other chunky white fish fillets, about 120g each (or use 2 small per person)
• 2 tbsp plain flour
• broccoli , to serve