Season the lamb shanks with salt and pepper and sear in a frying pan, colour all over. Place the shanks in a large casserole dish, or a deep roasting tin, deglaze the frying pan with a little of the red wine.
Place the onion, celery, carrot, garlic, bay and thyme in with the shanks cover with the red wine, top up with water or lamb stock if you have it, this is not essential.
Place a lid on and cook in an oven at 190c for about 3 hours or in till the lamb is falling from the bone.
Now start the diced vegetables, cut the onion, carrot, leek and celery into a 1 ½ cm dice square, once cut, sweat the onion, celery, carrot down in the butter, once the carrot is cooked to the bit, stir in the leeks and take off the heat. Leave to one side.
Once the lamb is cooked remove from the cooking liquor, allow to cool a little. In mean time strain the cooking liquor through a sieve and place back on the heat and bring to the boil.
Skim off any fat or impurities and reduce down to about 400ml liquid this will take a long time, about 1 hour.
While the liquid is reducing shred the lamb off the bone, it should just fall apart.
Peel the potatoes, wash and dice into 1 inch cut, bring to just under the boil in heavily salted water and strain.
Start again, cook the potatoes until just tender, strain and mash add salt, white pepper, butter and the egg yolks.
Once the cooking liquor has reduced add the tomato puree and Lea and Perrins and bring back to the boil. The liquor should coat the back of a spoon.
Now fold in the shredded lamb and the cooked diced vegetables, place in a 2inch deep baking dish, level out and top with the mashed potato bake in the oven until the mash topping takes on colour and is starting to go crisp.