Game Without Rules by Michael Gilbert

For two secret agents, there's no such thing as a quiet life in the countryside... 

In a peaceful Kent village, Mr Behrens lives with his aunt at the Old Rectory, where he plays chess and keeps bees. His friend Mr Calder lives nearby with Rasselas, a golden deerhound of unnatural intelligence. No one would suspect that they are in fact working for British Intelligence, carrying out the jobs that are too dangerous for anyone else to handle - whether it's wiping out traitors, Soviet spies or old Nazis - in these gloriously entertaining stories.