Blackmail Marriage by Penny Jordan

Prince Luc D'Urbino needs a wife - urgently. His Mediterranean principality is in turmoil, and only a royal wedding will solve the problem! Years ago Carrie Broadbent shared one night of passion with Luc, so now she's more than a little surprised when he returns and demands they marry...threatening to reveal a family secret that could ruin reputations and lives. Carrie is forced to accept Luc's proposal and all that it entails: staying by his side for better and for worse, as his princess and his lover....

Originally published in 2003