In early December 1967, workmen discovered what they thought was a lump of scrap metal while bulldozing a new road at The Tene. A second object seemed more interesting and they recovered it undamaged, selling it for £5. The new owner showed it to Leslie Matthews of the Manshead Archaeological Society in Dunstable, who immediately recognised it as an Iron Age firedog. He contacted John Moss-Eccardt at Letchworth Museum, who in turn informed the Inspectorate of Ancient Monuments, which sent an emergency team to begin excavation on 1 January 1968. The same team also investigated the north side of Clothall Road before it was widened later in the year.
Following this unexpected discovery, the Department of the Environment made funds available to John Moss-Eccardt to excavate in advance of building work at Brewery Field. In the following year, Ian Stead, who had led the team at The Tene, returned to look at the site of the proposed new Telephone Exchange in Walls Field. He also dug a series of 135 trial trenches by bulldozer on Upper Walls Common (now the Clothall Common estate), revealing the extent of the settlement to the north-east. In 1970 and 1971, he worked on a large area on the south-western edge of the common and in 1972, moved to Walls Field, to investigate an area proposed for a new school (that was eventually built on a different site, now Hartsfield School).
Ian Stead is one of the foremost British archaeologists specialising in the Iron Age. As well as his work at Baldock, he conducted major excavations at Braughing, near Puckeridge on the A10 in East Hertfordshire, and at King Harry Lane in St Albans, where he discovered one of the most important Iron Age cemeteries ever excavated in this country. He worked for many years at the British Museum.