I’m unsure on when the lamb comes out if the oven if you cook it overnight for the Shredded Lamb Salad?
Lamb is often served at Easter and Nigella's Warm Shredded Lamb Salad With Mint And Pomegranate (from NIGELLA BITES) is a low effort recipe for shoulder of lamb. The shoulder is marbled with fat so it is perfect for long, slow cooking and Nigella's recipe gives two options, to cook the shoulder overnight or a slightly quicker 5 hour option.
If you are using the overnight option then you should find that the lamb shoulder is ready by lunchtime the following day. If you put it in the oven at bedtime (up until midnight) then it should be cooked through and fall-apart tender by midday the following day. The advantage of this cut of meat is that it is very forgiving, so you can leave the lamb in the oven for a bit longer, if necessary, or let it sit out of the oven for an hour or so before serving. If removing from the oven then just loosely cover the pan with foil and leave it in a warm place. The lamb should, however, be served within 2 hours of being removed from the oven.