Hall of Mirrors: Bryant and May, Book 15

The year is 1969 and ten guests are about to enjoy a weekend at Tavistock Hall. The guests also include detectives Arthur Bryant and John May - undercover, in disguise and tasked with protecting Monty Hatton-Jones, a whistle-blower turning Queen's evidence in a massive bribery trial.

The house's owner - a penniless, dope-smoking aristocrat - is intent on selling the estate to a secretive millionaire but the weekend has only just started when the millionaire goes missing and murder is on the cards...