Portuguese discovered Australia. It is the other way around. The Dieppe maps prove (sic) that the Portuguese discovered Australia, and this throws a fierce bright light on our mysteries such as the Mahogany Ship". Later writers on the same topic take the same approach of concentrating primarily on "Jave la Grande" as it appears in the Dieppe maps, including Fitzgerald, McKiggan and most recently, Peter Trickett. Critics of the theory of Portuguese discovery of Australia, including A. Ariel, M. Pearson, W. A. R. Richardson, Gayle K. Brunelle and Robert J. King also concentrate on the "Jave la Grande" landmass of the Dieppe maps (see below). W. A. R. Richardson argues that Jave la Grande as it appears on the Dieppe world maps is at least partly based on Portuguese sources that no longer exist. McIntyre attributed discrepancies between the Jave la Grande coastline and Australia's to the difficulties of accurately recording positions without a reliable method of determining longitude, and the techniques used to convert maps to different projections. In the late 1970s, mathematician Ian McKiggan developed his theory of exponential longitude error theory to explain discrepancies, although he modified this position after a public exchange of opinion with W. A. R. Richardson. McIntyre's own theory about distortion of the maps and the calculations used to correct the maps has also been challenged. Both Lawrence Fitzgerald and Peter Trickett argue Jave la Grande is based on Portuguese sea charts, now lost, which the mapmakers of Dieppe misaligned. Both these writers try to compare the coastal features of Jave la Grande with modern Australia's, by realigning them. In 1994, McIntyre suggested that the writings of Pedro Nunes supported his interpretation of the distortion that occurred on the Dieppe Maps. Helen Wallis, Keeper of Maps at the British Museum, referred in 1988 to the interpretation "explosion" on the subject of the Dieppe maps. She herself argued the case for discovery of Australia by "a local Portuguese voyage otherwise unknown" seventy years before the Dutch, a chart of which was "presumably" brought back to Dieppe by the survivors of a French voyage to Sumatra led by Jean Parmentier in 1529–30. Cristóvão de Mendonça's role Cristóvão de Mendonça is known from a small number of Portuguese sources, notably the famous Portuguese historian João de Barros in Décadas da Ásia (Decades of Asia), a history of the growth of the Portuguese Empire in India and