Both men turned to look at her.

“The Holbein portrait in the Council Chamber. They were tapping on the wall just below it. And it’s a portrait of the Earl of Richmond!”

“You’ve got it,” said Battle, and slapped his leg.

He spoke with an animation quite unwonted.

“That’s the starting-point, the picture, and the crooks know no more than we do what the figures refer to. Those two men in armour stand directly underneath the picture, and their first idea was that the diamond was hidden in one of them. The measurements might have been inches. That failed, and their next idea was a secret passage or stairway, or a sliding panel. Do you know of any such thing, Mrs. Revel?”

Virginia shook her head.