He continued to collect materials and to revise and expand "Britannia" throughout his life. He drew on the published and unpublished work of John Leland and William Lambarde, among others, and received the assistance of a large network of correspondents with similar interests. He also travelled throughout Great Britain to view documents, sites, and artefacts for himself: he is known to have visited East Anglia in 1578, Yorkshire and Lancashire in 1582, Devon in 1589, Wales in 1590, Salisbury, Wells and Oxford in 1596, and Carlisle and Hadrian's Wall in 1599. His fieldwork and firsthand research set new standards for the time. He even learned Welsh and Old English for the task: his tutor in Old English was Laurence Nowell.