My Lady Love by Paula Marshall

A pauper may look at a queen... But he certainly can't marry one. That much was clear to Charles Shadwell, Viscount Halstead, who, after losing his memory, found himself employed as a stableboy by Nell Tallboys, Countess Malplaquet. Nor was that his only problem. Before his accident, Charles had wagered that the countess was no more virtuous than his faithless first wife. A bet he might win if the countess had her way!

Darling Amazon by Sylvia Andrew

Marriage is a desperate thing... Julia Marchant had made a fool of herself over Hugo, Marquess of Rostherne, when she was still a green girl. Now he had come back into her life because of a white lie she'd told her ailing father -- a lie that led him to believe that she and the marquess were betrothed. Unfortunately, Society got wind of the spurious engagement, and Julia and Hugo had no choice but to play out the charade...for now.