Showing Last Year's Nightingale by Claire Lorrimer

Clementine Foster is young, unbelievably innocent, and wildly in love with a man who doesn't even know of her existence. When, one golden summer night, she steps in front of his horse, he takes her with all the drunken arrogance of a young aristocrat used to having whatever he wanted. The repercussions of that night were to create bonds of hate, love, and tragedy in both their lives.

For the child that is born to Clementine ultimately appears to be the only legitimate heir to the Grayshot inheritance. And, according to the law of the times, she has no right to keep her child if Deveril wanted him.