From 1954 to 1976 van Geersdaele worked at the British Museum.[4] He began in the moulders’ shop, creating replicas of classical sculpture,[1] and rose to become a senior conservation officer in the British and Medieval department.[4] There he notably led the team tasked with making a mould, and later a fibreglass replica, of the Sutton Hoo ship,[5][6] a process he repeated in October 1970 with the Graveney boat.[7] Other work at the museum included the 1964 removal of a thirteenth-century tile kiln from Clarendon Palace,[8][9] a project in which, as with the Sutton Hoo ship,[10] he was assisted by Nigel Williams,[11][12] and the 1973 restoration of fourteenth-century wallpaintings from St Stephen's Chapel in Westminster Palace.[13] He also helped with excavations of the Longton Hall porcelain factory and the Broadstairs Anglo-Saxon cemetery.[2] During his time at the museum he also studied part-time towards a conservation diploma at University College London's Institute of Archaeology, which helped equip him to publish several articles on his work.[1][2]