Grilled Lobsters with Tarragon

Place the lobsters on their back shells on a wooden board. Quickly sever spinal cord by plunging a sharp knife through to back shell where body and tail of lobster are joined. Chop through the back shell fore and aft to cut into halves. When all lobsters are split into halves, remove and discard small sac below head. Remove and discard intestinal vein running down center