Another advantage of this method, particular when roasting chicken, is that you get a lot more juice. Yesterday, I rubbed a chicken (2.2kg) with a little butter, salted it, and stuffed it with a quartered lemon and with the cloves from a head of garlic. I pre-heated the oven at its highest setting, then turned it down to gas mark 6/200C, and put in the chicken, with the neck part of the giblets next to it. After 30 minutes, I turned down the dial to gas mark 3/160C. After another 30 minutes, I surrounded the chicken with peeled, sliced, washed and drained potatoes.
The chicken was ready after two hours in total. I removed it to a hot plate, which I kept on the grill shelf above the oven. It left behind plenty of juice, which I spooned off into a saucepan, with the neck.
I tossed the potatoes in the tin with some olive oil, and returned them to the oven (with the shelf raised a level) at its highest setting. After 20 minutes, I tossed them again. They were browned in half an hour. The chicken was still warm.
There was enough buttery, lemony sauce, which I warmed in the pan, for four.
The lamb above is studded with slivers of garlic and rosemary, rubbed with oil, salted, and roasted with a foil covering for three hours at gas mark 2/150C. (It browns in spite of the covering.) The procedure with the potatoes was the same as above.