Pierce each potato a few times with a sharp knife. Rub with a little oil and season the skin with salt. Heat the oven or air-fryer to 200C/180C fan/gas 4 and cook for around 1 hr 20 mins in the oven or 45 mins in the air-fryer – you can reduce this time by up to half if you microwave the potatoes for 5 mins beforehand. They should be crisp on the outside and fluffy in the middle.

Meanwhile, make the tuna crunch. Combine the drained tuna with the celery, onion, pepper, mayo, mustard, lemon zest and juice. Season with plenty of black pepper.

Cut a cross in the top of each potato and add 1 tsp of butter to each one. Serve with a bowl of the tuna crunch salad, and a selection of your chosen accompaniments on the side.