Curried mackerel with potatoes and spinach

1) Heat oven to 220C/fan 200C/gas 7.
2) Make a couple of slashes in both sides of the fish and rub with half the curry paste.
3) Heat the oil in a frying pan and fry the potatoes and onion for about 8 mins until starting to brown.
4) Stir the remaining curry paste into the potatoes, and fry for 2 more minutes.
5) Pour the potatoes and onions into a roasting try and top with the fish.
6) Roast in the oven for 20-25 mins until the fish and potatoes are cooked.
7) Remove the fish and keep warm.
8) Put the roasting tin over a high heat. Add the spinach to the pan with the potatoes and cook for 3-4 mins until completely wilted.
9) Serve with the fish.