Heat oven to 160C/140C fan/gas 3. Tip
the potatoes into a large roasting tin
with the olive oil, lemon and 100ml water.
Put the tin on a shelf under the lamb and
cook for 1½ hrs. When the lamb comes
out, give the potatoes a stir. Turn up the
oven to 220C/200C fan/gas 7 and cook
for a further 45 mins-1 hr. They won’t go
as crisp as roasties, so poke them with a
knife to check they’re cooked through.