Pre-heat the grill to hot. Line a baking tray with nonstick baking paper.
Rub the fillets of sole with the olive oil and season well. Arrange on the lined baking tray and drizzle over the lemon juice. Grill for 3-4 minutes until opaque in appearance.
Remove from the grill and allow to rest for 1 minute.
Slide onto serving plates and garnish with the lemon slices and chopped tarragon. Finish with a sprig of tarragon and some more seasoning before serving.