The Beggarstaffs were:
Sir William Nicholson, English, (1872-1949) & James Pryde, Scottish, (1866-1941)
Under the pseudonym, they virtually created the modern poster, with clear outlines and large areas of flat colour. Perhaps the most influential graphic designers of all time.
William Nicholson's woodblock prints of the 1890's were amongst the most revolutionary British print images of the era. They used a treatment of form, with a stylised simplification of shape, and a handling of perspective and picture space which had had no precedent in British art. Influences of Japanese art, and a parallel thinking to, if not a direct knowledge of, the ideas of Toulouse Lautrec and of the Nabis painters in Paris at the same period can certainly be felt, although there is no record that Nicholson had actually studied either at this date.
For more information, check out a book called "The Beggarstaff Posters" by Colin Campbell.