As a young man he was a researcher for the Nottingham Borough Council and became a contributor to the English Historical Review.
Having worked for many years on early charters, in May 1898 Stephenson delivered the Sandars Lectures at Cambridge on the subject of 'The Anglo-Saxon Chancery'.
[4] A fellow and librarian of St John's College, Oxford, from 1904 until his death, he was the mentor of Frank Stenton.
[4] In 1905, while working on records kept at Belvoir Castle, Stevenson discovered evidence that in March 1613 (a few months before the Globe theatre burnt down during a performance of Henry VIII), William Shakespeare and Richard Burbage, who had some skill as a portrait painter, were each paid forty-four shillings in gold for creating and painting the Earl of Rutland’s emblem.
This decorative emblem was to be used at a festive tournament later that month at Whitehall in London to mark the accession of King James I ten years earlier.