Living as we do in the U.S., I don't have Nigella's, but here's ours:
2 1/2 tbsps Dijon mustard .
2 tbsps honey .
2 c ginger ale .
1 pinch cayenne pepper .
1 (3-4 lb) boneless ham, fully cooked .
1 c white wine .
2 tbsps molasses
Directions
Preheat oven to 300F degrees F.
Place ham on a rack in a roasting pan.
In a saucepan mix wine, mustard, molasses, & cayenne pepper.
Bring to simmering.
Simmer, uncovered for 6 mins.
Stir in ginger ale.
Pour glaze over ham.
Bake 1 hr (I usually cover loosely with foil wrap, afraid of drying it out).
Increase oven temperature to 325F degrees F.
Bake 1 hr more (remove foil wrap covering), basting ham every 15 mins.
Brush ham with honey.
Bake 15 mins more.
Slice & serve.