She was already involved with early maps of the South Seas for her Oxford thesis when she was appointed assistant to R. A. Skelton, Superintendent of the Map Room at the British Museum, in 1951. Together, they created a national institution out of the map library. Behind the formidable door in the North Wing, with its intimidating bell and uniformed attendant, the visitor encountered infinite help and the friendliest atmosphere.
It was natural that Wallis, who had the vision of transforming the museum's collections into a National Map Library, should be appointed successor to Skelton in 1967. By the time that she retired in 1986 she had added an international to her national reputation.
Side by side with her administrative duties, Wallis furthered the study of the history of cartography academically and its development organisationally. Among her research publications the two volumes of Cartaret's Voyage round the World 1766-1769 which she prepared for the Hakluyt Society and an edition of Jean Rotz's Book of Hydrography, 1542 stand out. Together with A.H. Robinson, she published the study Cartographical Innovations. A Historian's Guide to Early Maps of the British Isles appeared shortly before her death.
She had especial interests in the Vinland Map, the Dieppe Maps of North America and the voyages of Captain Cook, about all of which she wrote. Exhibitions at the British Library made demands upon the map collection as well as calling for contributions to catalogues. Wallis was as much at home in the great cartographic collections at Washington and Los Angeles as she was among those of Europe. She helped with the transfer of three important exhibitions to the United States - "The American War of Independence" (1975), "The Voyage of Francis Drake" (1977) and "Raleigh and Roanoke" (1988).
Both national and international cartographic organisations claimed her allegiance. Wallis was the first woman president of the British Cartographic Society. From 1976 to 1987, she was the chairman of the standing commission on the history of cartography of the International Cartographic Association and in 1986 she became president of the International Map Collectors' Society. The Geography and Map Section of the International Federation of Library Associations owes much to her initiative as a founder member. From 1972 to 1988 she was chairman of the Society for Nautical Research.
Helen Wallis had an exceptionally wide circle of friends. There were those from her childhood, which was spent with her twin brother in north London, where her father had been a headmaster; those from the musical circles which she much enjoyed; from St Paul's School for Girls, in London; from St Hugh's and the School of Geography at Oxford, where she added a DPhil to her MA in 1954. Her geographical interests were kept abreast of the times through membership of the Institute of British Geographers and she was for many years an invaluable member of the Frederick Soddy Trust. But it was on her retirement that the friendships that she had struck up became manifest. She was almost overwhelmed by the number of invitations to fill visiting lectureships and chairs. She found those from Australia, New Zealand and the United States irresistible.
The honours and distinctions that came her way were many and varied. They ranged from an OBE in 1986, an Hon DLitt from Davidson College, North Carolina, and an Honorary Fellowship of Portsmouth Polytechnic to the Gold Medal of the British Cartographic Society and the Caird Medal of the National Maritime Museum.
Throughout her professional life, Wallis had been closely associated with the Royal Geographical Society. She served on the council, was a member of the Library and Maps Committee for over 20 years and its chairman for nine. Her friendliness was especially appreciated by the staff of the society's house in Kensington. In 1988, she became an honorary vice- president. She enjoyed the convivial company of the Geographical Club, to the ranks of which she was an early recruit when it opened its membership to women.
Beyond her academic and other achievements, she will be remembered for her enthusiasm, her modesty, the light touch with which she conducted her affairs - indeed, the fun that she seemed to get out of life. It was an inspiration to encounter the same optimism and quiet laughter only a few days before her death in St John's Hospice, in St John's Wood, the spirit of which was one of her strong Christian beliefs.
W. R. Mead
Helen Margaret Wallis, historian of cartography: born Barnet 17 August 1924; OBE 1986; died London 7 February 1995.