Slice the lamb neck into 1cm slices, season well then place in the flour. Shake off the excess.
Heat a large frying pan with the olive oil, and when smoking, add the herbs then brown the lamb slices on each side. Note, you will need to do this in two batches so as not to overcrowd and cool down the pan. Deglaze with the malt vinegar then a splash of stock. Remove the lamb slices and juices and set somewhere warm to rest.
Heat the olive oil in a pan. When warm, add the shallots and table salt and cook gently, until soft but not coloured. Add the malt vinegar and cook for a further 5 minutes, until syrupy. Add the mustard, stir well then add the peas. When warmed through, add the mint.
Rub the olive oil into the baguette and rub with garlic. Layer the lamb slices on the base of the baguette, then pour over the sauce and juice. Add the pea mix then top with the other half of the baguette. Serve whilst warm.