Roast Topside with Marmalade Glaze

Preheat the oven to Gas mark 4-5, 180-190°C, 350-375°F. 
Place the topside joint on a chopping board, make several slits over the joint and season and rub with the mustard. Push the garlic slivers into the slits. 
Place the joint on a metal rack in a large roasting tin and open roast for the preferred, calculated cooking time, basting occasionally with any rich beefy juices. 
In a small bowl, mix together the marmalade, orange juice and parsley.  Divide the mixture between two separate bowls.
20-25 minutes before the end of the cooking time remove the joint and brush with the marmalade mixture from one of the bowls to glaze and return to the oven.
Serve the beef with roasted, new potatoes, parsnips, seasonal green vegetables, gravy and the untouched glaze from the second bowl.