Under a statute of William III. prosecutors who had secured a capital conviction against a criminal were exempted from all parish and ward offices within the parish in which the felony had been committed. Such persons obtained a Tyburn Ticket, which was duly enrolled and might be sold. The Stamford Mercury (March 27th, 1818) announces the sale of one of these tickets for 280. The Act was repealed by 58 Geo. III., c. 70.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894