Preheat the oven to 190C/375F/Gas 5 (170C fan)
Peel and cut the onion into 8 wedges and put 2 in the cavity of the pheasant along with a few sprigs of thyme and bay leaf. Put the remaining onions in a small roasting pan.
Smear the butter over the pheasant breast and season the whole bird with salt and pepper then lay the bacon over the top of the breast and lay the pheasant on top of the onions in the roasting tin.
Put the roasting tin on the middle shelf of the oven and roast for 45-55 minutes until the thigh juices run clear when pierced with a skewer. If the pheasant is browning too much cover with foil.
Remove from the oven and put the pheasant to rest on a warm plate. Spoon any fat from the juices and pour in the wine and a sprig of thyme and put on a high heat to boil until it is reduced by a third. Season and stir in the redcurrant jelly and pour into a warmed jug.
Carve the pheasant and serve with the onions and warmed jus. This dish goes well with braised red cabbage, roast pumpkin and roast potatoes.