He will be remembered too for the generous input of his guiding hand at the Rathmichael summer school, a milieu through which both schoolchildren and adults were introduced to archaeology, many later graduating to the professional ranks thanks to Leo's encouragement.
Although Leo was four decades involved in the promotion of archaeology, and in the important excavation of the  site at Kilpatrick, Co. Westmeath, it was about ten years ago that he finally took the plunge, retired from his headmastership and set up a company, Arch-Tech, which mainly specialised in the archaeological assessments of threatened sites. In partnership with Frank and later Tim Foley, he built up a strong team that included his son Ronan and was anchored around his secretary, Mary Harkin, and himself, an achievement which he was justly very proud. Among his excavations were Kilpatrick, Co. Westmeath, Swords Castle, Co. Dublin and Ushers Quay and Collins Barracks, Dublin. He did countless archaeological impact studies and site assessments.

Leo produced a steady stream of learned articles that ranged from the discovery of new sites at Tara to the report on his excavation on Ushers Quay and a cluster of articles on his beloved Kilpatrick. His main publications are significant because of their concentration on settlement sites and patterns that he derived from aerial photography. Others will endure because of the primary work presented in them; still others because of their comment value.