Her Royal Highness by William Le Queux

Hubert Waldron, a smart figure in his diplomatic uniform, strolled along the corridor, followed at a respectable distance by the neatly-dressed waiter until, at a convenient point, the diplomat halted at the junction of two corridors, as though in doubt. Pucci was at his side in an instant.

"I learnt only half an hour ago, signore, that there is a plot against you! " he said. "Signor Ghelardi is your enemy. You were attacked by the two assassins whom he bribed, but the conspiracy failed. Be careful. Exercise the greatest caution, signore -- I beg of you."