Heat a grill pan or wire rack over the heat or coals of a barbecue.
For the dressing, whisk the vinegar, mustard and olive oil together in a bowl until fully emulsified. Season with salt and pepper, adding a little lemon juice if desired.
For the sardines, lettuce and samphire, trim the brown root off the bottom of the lettuce and then cut into quarters. Brush with a little olive oil and place on the grill until charred and toasted.
Blanch the samphire in a pan of boiling water for twenty seconds, then remove from the water with a slotted spoon.
Brush the sardines with a little oil and season with the sea salt.
Put the sardines onto the hot grill or barbecue and cook until the skin is charred; then turn over to cook the other side of the fish.
When cooked flake the fish into a bowl with the gem lettuce, parsley and and lemon zest. Add the samphire and dress with the red wine dressing.