Great Britain 1840 1d black plate 4, the cancellation removal trial of 1840, SG2Great Britain 1840 1d black plate 4, the cancellation removal trial of 1840, SG2 As early as January 1840 the treasury was advised that the red handstruck "PAID" markings could be removed from covers by the application of creosote oil. As a result of this alarming fact the treasury instructed experiments to be undertaken on the ink used for cancelling postage labels. The Penny Black was so well printed in such fast colours that it was a fairly simple