Chop the thyme leaves and infuse into the olive oil with the lemon zest while you prepare the dish.

Boil the potatoes in their skins until soft, drain and peel once cool enough to handle. While still warm, cut into thick slices and dress with salt and a little of the flavoured olive oil.

On a serving platter or on individual plates, spoon the mayonnaise and spread to almost cover the plate.

Rinse the capers of salt and pat dry with paper towel. Fry the capers in the olive oil until they open up and become crispy - a couple of minutes then drain off the oil.

To finely slice the tuna, I find it easier to wrap the fillet tightly in cling wrap and freeze it for 1/2 hour so that it becomes firm. Slice the tuna very thinly and lay out on the mayonnaise.

Arrange the potatoes on top and scatter with capers, salt and the remaining flavoured olive oil. Serve at once.