Maris pipers, always.
I parboil in salted water with a bit of apple cider vinegar, which makes the surfaces go a bit flakey
Drain, shake to bash them up a bit, then leave them to cool until they stop steaming.
Season.
Heat oven to 220c fan. Fat in roasting tin (I use goose, duck or dripping depending on what meat we are having, with some real butter which makes them go really golden). Fat in oven for at least 5 mins until sizzling.
Remove tin from oven and pour hot fat into a jug (not plastic!), add potatoes to hot tin then pour over the fat making sure every spud is coated. I find this quicker than basting with a spoon so the fat stays hotter.
Back in oven for 45 to 60 mins depending on the size of the potato chunks. I turn the temperature down to 200 after 30 mins, and I turn them quickly once.
We are lucky to have a double oven now so they go in on their own, but previously I would cook them after the meat was out and resting. If you've got a bird in the oven the steam ruins the spuds.
I think the key things are the right variety of potato, letting the steam come off after parboiling so they don't end up soggy, and having really really really hot fat. And not opening the oven too much.
I want one now.