Take it slow and easy with a roast lamb you can throw in the oven and forget about. The white wine gravy makes itself.
Preheat the oven to 170C/325F/Gas 3.
Pour the oil into a large, sturdy roasting tin and set it over the hob. Season the lamb then roll it in the flour. Brown the lamb all over in the hot oil for 5-10 minutes.
Add the onions and cook for a further 5-10 minutes, turning the lamb and stirring the onions until both are nicely browned.
Add the garlic, white wine, stock, oregano and redcurrant jelly, bring to a simmer and cook in the oven for 3-3½ hours, basting now and again with the liquor. There should be a good quantity of wine left in the bottom of the tin to serve with the lamb but if you feel it is getting too dry, just cover with foil.
Take the lamb out of the tin and place on a large board to rest in a warm place. While the lamb is resting, sit the tin back on the hob and simmer the pan juices for a few minutes, reducing the liquid, if there is a lot, to make a tasty gravy.
Cut the lamb into thick slices - you'll find the meat falls away from the bone so you may end up with more chunks than slices.
Serve with creamy mashed potatoes and the wine gravy.
