The Heiress Objective by Regina Scott

Wealthy Regency heiress Eugennia Welch is afraid to tell her bluestocking friends the truth: she secretly wishes a handsome prince would ride in and propose marring. When charming Corinthian Kevin Whattling does just that, she is stunned. He claims to have admired her for some time, but only came forward now because he must marry an heiress to discharge his debts. How can she believe anything he says?
Once one of the most successful intelligence agents among the aristocracy, Kevin Whattling gave up his commission when his younger brother was killed in an illegal boxing match. Now deep in debt, his only hope is to marry a wealthy wife. But as he tries to convince Jenny he is besotted, he finds himself falling under her spell. When a danger from Kevin’s past threatens them both, they must trust each other to win a love far greater than any fortune.