Matt Williamson – one of the chefs behind the new Camper Van Cooking cookbook – admits: “Cooking fish over a fire can be a little bit difficult, because you want the temperature to be just right.”

That’s why he particularly likes this recipe when camping – all the other ingredients are ready to go, so you can “just concentrate” on getting the fish right.

“We could feed a real crowd with that,” Williamson adds. “This is one that you can dial up and easily do for four people or eight people, if you can get hold of all the fish and stuff. It’s quite an easy one to put together.”

Fried mackerel recipe, with horseradish butter, gherkins and lettuce in brioche buns

Ingredients:(Serves 4)

4tbsp butter, softened2–4tbsp horseradish, to taste4 large or 8 small mackerel fillets1 soft round lettuce, leaves separated4 large gherkins, slicedSalt and black pepper4 brioche buns (or any soft roll), split open, to serve

Method:

1. Beat the butter and horseradish together in a bowl, adding pepper to taste, then put the mixture to one side.

2. Season the mackerel fillets on both sides and grill them over a high heat, skin-side down, for two minutes. Carefully flip the fillets over with a spatula and cook for another one minute, until just cooked through. (Cook in a pan with a splash of cooking oil, if you prefer.)

3. Lightly toast the inside of the rolls on the grill, then generously spread each with the horseradish butter. Add lettuce and gherkins to each bun, then finally the cooked mackerel, sandwiching shut to serve.

Camper Van Cooking by Claire Thomson & Matt Williamson is published by Quadrille, priced £20. Photography by Sam Folan. Available now.