Help! Reducing temperature for leg of lamb to increase cooking time?!

[docket]

Have royally cocked up timing and put a slow roast Moroccan lamb leg in the oven an hour early for guests tonight. It is supposed to cook for 3hr 35mins at 160. Is there a way of gauging (guessing!) how much longer I can cook it without it drying if I lower to say 150? I need to buy at least half an hour. Any ideas? Much appreciated!

Heeeeeeelp!

Drop the temperature now to 150. Take the lamb out after 4 hrs, wrap it loosely - not tightly and not sealed - in foil. It will stay hot.

Second that, drop temp to 150. If there's nothing else in the oven you could turn it off and just leave the meat in for a few mins (say 15) after 4 hours or so.

Brilliant, thanks so much for replying