In the United Kingdom another line of ceramic armour development had been started in the early 1960s, meant to improve the existing cast turret configuration of the Chieftain that already offered excellent heavy penetrator protection; the research by a team headed by Gilbert Harvey of the Fighting Vehicles Research and Development Establishment (FVRDE), therefore was strongly oriented at optimising the ceramic composite system for defeating shaped charge attack. The British system consisted of a honeycomb matrix with ceramic tiles backed by ballistic nylon, placed on top of the cast main armour. In July 1973 an American delegation, in search of a new armour type for the XM815 tank prototype, now that the MBT-70 project had failed, visited Chobham Common to be informed about the British system, the development of which had then cost about £6,000,000; earlier information had already been divulged to the US in 1965 and 1968. It was very impressed by the excellent shaped-charge protection combined with the penetrator impact damage limitation, inherent to the principle of using tiles. The Ballistic Research Laboratory at the Aberdeen Proving Ground, which later became a part of the Army Research Laboratory, initiated the development of a version that year named "Burlington", adapted to the specific American situation, characterised by a much higher projected tank production run and the use of a thinner rolled steel main armour. The increased threat posed by a new generation of Soviet guided missiles armed with a shaped charge warhead—as demonstrated in the Yom Kippur War of October 1973, when even older-generation missiles caused considerable tank losses on the Israeli side—made Burlington the preferred choice for the armour configuration of the XM1 (the renamed XM815) prototype.