Inspector Sloan #3
On a stately home public tour, a mischievous boy lifts the visor on a suit of armor - and finds a corpse. Inspector Sloan and inadvertent joker Constable Crosby must sort out who stashed the body and why. Clues include a ne'er-do-well nephew and attempted blackmail. The key is tea served to two batty great-aunts.
"Catherine Aird is the pseudonym of novelist Kinn Hamilton McIntosh. She is the author of more than twenty crime fiction novels and several collections of short stories." - Wikipedia