It was a boneless rolled rib roast, about 1.6 kg. I just heated the over to its highest possible temperature (270C in this case), and placed the meat in, on a rack over a roasting tin.
After ten minutes, I turned the oven down to ~70C.
And I let it cook for the next nine hours.
Before taking it out of the oven, I checked how hot the core of the joint was. 69C.
I then kept it warm (about 60C) while I then cooked the rest of the meal - roast tatties, steamed asparagus, and gravy.
The meat was delightfully tender, and full of flavour. There were pretty well no juices in the pan at all, it had all stayed in the meat.
I think I like this oven.