William Francis Grimes had worked for the National Museum in Cardiff until just before the Second World War when he went to the Ordnance Survey (and took part in the Sutton Hoo excavations). He had a distinguished career with a strong interest in prehistory (see D.W.J. Gill, ‘William F. Grimes’, The making of a prehistorian’, Bulletin of the History of Archaeology (2000) [here]). He was invited to prepare two paper guides to two prehistoric sites in Wales:
In 1953 Grimes was still the Director of the London Museum, but in 1956 he had been appointed Director of the Institute of Archaeology in London. He had conducted excavations at Pentre-ifan. Wilfrid J. Hemp had conducted work at Capel Garmon.
For further details about Grimes see Gill in Oxford Dictionary of National Biography.