The Theft of Magna Carta — John Creasey

An international gang, English and American, work out a ruthless scheme for stealing one of England's priceless treasures; the Sarum Magna Carta. In its place in Salisbury Cathedral Library it is protected by the most sophisticated security measures, but that won't be allowed to get in their way. Pitted against the gang, Superintendent Roger West of Scotland Yard has to recover the document and solve one of the most ambitious crimes met in his long career.