One of the extant observation posts at Ynyslas. The two viewing slits at the front of the shelter once overlooked test firings over the sand flats of the Dyfi estuary. In front of the brick-built shelter are several concrete bases for instruments which record the flight path of the missile or perhaps an early radar guidance system. The observers at MOS EE AA Ynyslas were drawn from the women's Auxilliary Territoiral Service (ATS). In a letter written in June 1946 by the Chairman of the Guided Projectile Working Committee, Major L W Jubb, he noted how much the Superintendant of the Experiments, Lt Col T L G Todd missed these highly skilled ladies after mobilsation.