Put the lamb in a bowl.
Add all the marinade ingredients except the oil, stock, gelatine and sugar.
Cover and leave to marinate for 24 hours, turning occasionally.
Drain the lamb and dry on kitchen paper (paper towels).
Heat the oil in a flameproof casserole (Dutch oven) and fry (saute) the meat on all sides to brown.
Remove from the pan.
Strain the marinade, reserving the liquid.
Add the marinade vegetables to the pan and fry, stirring, for 2 minutes.
Return the meat to the pan.
Pour the marinade over (including the rosemary) and add the stock and sugar.
Bring to the boil, reduce the heat, part cover and simmer over a very gentle heat for 2 1/2 hours or until very tender.
Do not boil fast.
Leave to cool in the liquid.
Remove the meat, wrap in foil and chill.
Skim off any fat from the surface of the cooking liquid, then strain into a clean pan.
Sprinkle the gelatine over and leave to soften for 5 minutes.
Heat gently, stirring until the gelatine has completely dissolved.
Meanwhile, steam the prepared spring vegetables or cook in a little boiling, lightly salted water until tender.
They must be soft or they will harden when in the jelly.
Drain, rinse with cold water and drain again.
Pour a thin layer of the gelatine stock in the base of a lightly oiled 1.5 kg/3 lb loaf tin (pan) or terrine.
Arrange a layer of vegetables lengthways in it and chill until set.
Carve the meat into slices, discarding the string, and arrange down the centre on top of the set vegetables.
Arrange some more vegetables down the sides.
Pour enough of the gelatine stock over to cover and chill again to set.
Heat the remaining stock, if necessary, to melt.
Arrange the remaining vegetables over the top and pour over the remaining gelatine stock.
Chill until firm.