Warm Mackerel and Cucumber Salad

• 1 cucumber
• salt
• 1 lb / 455 g mackerel fillets

Cut the cucumber in half lengthways and scoop out the seeds. Slice the cucumber very thinly on a mandolin or use the slicing disc of a food processor. Place the slices in a colander or sieve, sprinkle with a little salt, and leave to drain for 1 hour. Meanwhile prepare the fish. Remove any bones with tweezers, and cut the fillets into neat oblique slices about