Put the meat slices between two layers of clingfilm and beat gently to flatten.
Spread one side of each slice with mustard and season with salt and pepper.
Stuff the prunes with the olives if desired and put two stuffed prunes in the centre of each meat slice. Roll up the slices and secure with cocktail sticks.
Spread the outside of the rolls with the Marmite. Heat the oil and butter in a black pot and fry the rolls until golden brown.
Heat the wine and stock and pour over the meat. Add the bouquet garni, reduce the heat, cover and simmer until the meat is tender (about one hour).
Add the lemon juice and adjust the seasoning if necessary.
Serve the beef olives with pap.