Heat the oven to 200C/fan 180C/gas 6.
Add the flour, salt, mustard powder, paprika and cayenne to a bowl. Toss the whitebait in to coat with the spiced flour.
Heat a pan with no more than 1/3 full of oil. Fry the whitebait, in small quantities, for 4-5 minutes until it becomes crispy.
Drain on paper towels and heat up in a low oven while you fry the rest.
Serving Suggestions: Serve the devilled whitebait with garlic mayo, a sprinkle of salt and lemon wedges to squeeze over.