Romancing the Rifleman. The Astley Chronicles, #6

She's the one woman Harrington Astley can never have. Lady Diana Latimer might be everything Harrington Astley has ever wanted. But her older brother, the Duke of Trevissick, despises him, and would never give his approval for them to wed. The beautiful girl who makes him feel like he's more than just cannon fodder is as unattainable as a star in the sky. Diana Latimer has had it with fops and fortune hunters. Making her London debut seemed like a lark three years ago.
But after her brother saddled her with an absurdly large dowry, Diana has found herself besieged by fortune hunters. There's only been one man she's truly liked-Harrington Astley, a handsome army lieutenant with an irreverent sense of humor. Now Harrington is back in London, but thanks to her brother's meddling, he's convinced that nothing can ever come of the attraction flaring between them. When the Foreign Office asks Harrington to attend a house party to try to ferret information out of a Swedish prince he befriended during his last deployment, Diana sees her chance.
Harrington doesn't speak a word of Swedish. But Diana does. Of course, a young, unmarried lady cannot attend a house party without a chaperone. which is why she informs Harrington that they need to marry. For King and country. Sometimes you have to fake it 'til you make it! Harrington promises Diana's brother that they will annul their fake marriage just as soon as their mission for the Crown is complete.
But Diana never agreed to that plan, and she's not giving Harrington up without a fight. She's going to do everything within her power to seduce her husband and turn their fake marriage into a love that lasts a lifetime. Please note that the heat level is red hot!