Braised peas with bacon, lentils & cod

INGREDIENTS

• 25g butter
• 4 sustainable cod fillets, about 100g/4oz each, skin on
• 2 tbsp olive oil
• 4 thick slices of back bacon , cut into matchsticks
• 300g shelled peas (fresh or frozen)
• 410g can lentils , drained and washed
• 2 lemons , 1 juiced, 1 quartered
• large handful mint leaves, roughly chopped