Being a potato aficionado, I learned sometime ago to produce really crispy skins and light fluffy insides by using the already mentioned olive oil and sea salt (although I also use the larger grained Kosher salt) and place the gem into a sizzling 500 degree F (I'm in the U.S., you do the math) oven for about 45 minutes. Absolutely, positively don't puncture the skins. Additionally, to insure the best product we use a light skinned baker spud rather than the red skinned ones. Not sure what you call them in the U.K. Don't wrap them in anything, except your own skin at the appropriate time...