Editors. "Conspiracy to release Perkin Warbeck from the Tower is discovered". The Literary Encyclopedia. First published 01 November 2010
[http://www.litencyc.com/php/stopics.php?rec=true&UID=14010, accessed 22 May 2013.]
The authorities discover that the Earl of Warwick (a genuine claimant to the throne) and fellow prisoner Perkin Warbeck had attempted to escape from the Tower of London, and the pair are re-imprisoned.