Traitor's field - Robert Wilton

It is 1648 and Britain is at war with itself. The Royalists are defeated but Parliament is in turmoil, its power weakened by internal discord.
Royalism's last hope is Sir Mortimer Shay, a ruthless veteran of decades of intrigue who must rebuild a credible threat to Cromwell's rule, whatever the cost.
John Thurloe is a young official in Cromwell's service. Confronted by the extent of the Royalists' secret intelligence network, he will have to fight the true power reaching into every corner of society: the Comptrollerate-General for Scrutiny and Survey.