Alan William Halliday Pearsall ISO, (born in Leeds on 14 November 1925 - died in London on 31 March 2006) was a naval and railway historian, who served for thirty years from 1955 to 1985 on the staff of the National Maritime Museum, Greenwich.
After demobilisation and a year of recovery from tropical illness, Pearsall went on to Trinity Hall, Cambridge, where he read history.
Encouraged by Graham, Pearsall took a position as a general assistant at the National Maritime Museum in 1955, rising to become Curator of Manuscripts in the 1960s, and then Historian, before he retired in 1985.
On his retirement, he was appointed to the Imperial Service Order in recognition of his wide-ranging knowledge of five centuries of British naval history and, as one obituarist characterised it, "his extraordinary value as adviser, teacher and scholarly oracle to colleagues at Greenwich, and to the wider specialist communities and information-seeking public that the museum serves".
Most importantly, his scholarly and informative advice was acknowledged in hundreds of works written by three generations of naval historians.