I baked my “jacket” potatoes in the British style rather than the American one since the commenters were concerned about me making the potatoes “right.”
I found a recipe from A Cup of Jo that involves cutting a cross into the potatoes before putting them in the oven and letting them cook at 400 degrees for two full hours. Then, you take them out, deepen the cuts, and put them back in for another 10 minutes. I’ve never let a potato bake this long, usually because I’m standing by the oven impatiently waiting for it to be soft enough to eat.