Pre-heat the oven to 200 °C/400°F/gas mark 6.
For the jus: In a roasting tray, sear and colour the bones in olive oil for about 6-8 minutes on top of the stove turning occasionally. Place into the oven and roast for 10 minutes. Add the chopped onion and cloves of garlic and return to the oven for another 6 or so minutes. Remove any excess oil. Add the white wine to the roasting tray and scrape the bottom to remove any caramelsied juices, reduce by 2/3 then add the chopped tomato, tomato pur, e, rosemary and thyme, then sweat for 3 or so minutes until softenend. Add the water then transfer all to a saucepan, bring this to the boil, skim, and simmer for about 15 minutes. Strain through a fine seive and reduce to taste. If you get the taste that you require but not the texture just thicken the jus with a little diluted arrowroot. Taste and season with salt and pepper, set aside.
For the breadcrumbs: Mix all the ingredients (except the mustard) in a food processor. Slowly pour in the olive oil until the breadcrumbs become 'sandy' in texture. Season with salt and pepper. Set aside.
Heat 2 tbsp of olvie oil in a saut, pan and sear the meat on its side for 1 minute until lightly coloured, then sear on its back for another 3 minutes. Place the best end of lamb fat side down and roast for about 12 minutes. Season with salt and pepper. Remove from the oven and spread the mustard all over the lamb (not on bones), using the back of a spoon. Then press the best end in the breadcrumbs until it is completely coated.
The rack of lamb may be prepared to this stage two to three hours in advance. (It should be allowed to cook for up to 8 minutes to reheat properly before being served if not used immmediately).
Roast again in the oven for another 6 minutes, remove the lamb, allow to rest on warm plates for 2-3 minutes, before serving.
Per serving: 122 Calories (kcal); 11g Total Fat; (90% calories from fat); 1g Protein; 2g Carbohydrate; 0mg Cholesterol; 117mg Sodium Food Exchanges: 0 Grain(Starch); 0 Lean Meat; 0 Vegetable; 0 Fruit; 2 Fat; 0 Other Carbohydrates