Round fish include the ever-popular cod, haddock, sea bass and mackerel to name but a few. The size of knife you will need depends on the size of the fish – the bigger the fish, the longer the blade required. A round fish will produce two fillets which will serve 1 or 2 people depending on the size of the fish.

Before you begin, make sure that your fish has been scaled and gutted. Ask your fishmonger to do this for you if you would prefer not to clean up – scaling fish is a messy business.

When you have mastered this technique, why not have a go at Robert Thompson's steamed fillet of sea bream with nage of Cornish oysters, tomatoes and cucumber and herb gnocchi or Simon Hulstone's pan-fried sea bass, butter spinach, clams, poached cod cheeks and fish sauce.