Preheat the oven to 220C/425F/gas 7 and place in it a large roasting dish with the oil in it, letting the oil melt and get sizzling hot while you parboil the potatoes. Chop the potatoes into medium-sized chunks (about 3-4cm in width). Bring a large pan or stockpot of slightly salted water to the boil and simmer the potato chunks in it for about 8-10 mins, until starting to give way to the prod of a knife. (This is the key to getting the softness of the inside of a perfect roast potato.)

Drain the potatoes and let them steam dry for a minute or two, then toss then in the colander to slightly "dent" them (giving some of them a bash with a fork to damage them can be great, too). To ensure extra crispness you could add an optional tablespoon of flour or polenta here and toss to coat, but it is not 100% necessary. Very carefully remove the roasting dish of oil from the oven and place the hot potatoes straight in (it will sizzle!). Toss with a spoon to coat the potatoes as much as you can, then return to the oven (don't add the salt at this stage if you want crispy-on-the-outside potatoes).

Roast for about 40-50 mins, until the potatoes are golden and soft and fluffy on the inside. Add the salt and pepper and return to the oven for 5 more mins. Serve hot out of the oven (the longer you leave them the less good they will be). Bask in the compliments! ;)