For the dressing, whisk the horseradish, vinegar and mustard together, then slowly whisk in the oils. Season then add about 1½ teaspoons of each herb.

Lightly brush the grill with oil and preheat on the hob on a low to medium heat. Test the temperature of the pan – see Cook’s Notes – before adding any food.

Trim the spring onions if necessary then, once the pan is hot, add to the grill and cook for about 1½ minutes on each side until nicely charred in places but retaining a little bite.

Brush the mackerel fillets with oil and season. Grill skin-side down first for about 1 to 1½ minutes or until nicely coloured. Turn over and cook for about 1 more minute. Remove from the grill and place one on each plate.

Lightly dress the salad ingredients with about half the dressing and divide between plates.

Drizzle the rest of the dressing around, sprinkle on the remaining herbs and serve.

Cook's Notes

To check if the grill is hot enough add a few drops of cold water to the hot surface. If it sizzles and the water evaporates almost immediately, it is hot enough and ready for use. If the water produces steam and has no sizzle, heat the pan for a little longer and repeat the test again.

Do not heat the empty grill for more than two minutes to avoid overheating.

Salmon or rainbow trout fillets would also work well in the recipe or try grilling two large, whole mackerel instead of fillets.