The 2d blue (from plate 1) went on sale at a small number of British Post Offices on 6 May 1840 and became valid for postage on the same day. The design was exactly the same as the 1d black.
In 1841, the design was altered to include two white lines (under Postage and above Two Pence).
Only four printing plates were used in the entire lifetime of the imperforate 2d stamps - two without white lines and two with.
Although superseded by later issues, these stamps remained valid for postage until all stamps bearing the image of Queen Victoria were finally de-monetized in 1915.