This has sprung from having recently seen the 1934 film, though I am planning to read the book when I get hold of it. It's influenced by the film then basically, so I apologise for any errors because of that. Hopefully this isn't committing treason with the characters.
Percy is sitting in the middle of a grassy field, part of the lands surrounding the Blakeney estate, his horse placidly cropping the grass nearby.
It is coincidence Marguerite has chosen this way to bring her own horse, alone. Not entirely proper, she knows, but she hardly cares.
She was unaware he had returned from town. A genuine visit this time; he swore truly to her, now she was aware of his other identity, and the oft used excuse of town or other estates being the norm for his absences to France.
Her horse dances slightly beneath her, impatient with the inactivity, but she controls it quickly. If she didn't know better she would have been shocked – Sir Percy Blakeney, one of the biggest fops in London, sitting in his finery on the grass like a 'commoner', as they would have likely have termed it. But he sits there so peacefully, looking out over the hills as naturally as it came that she is loathe to disturb him, content instead to watch him as he is, not playing up to the London crowd for once.
If only they knew him as she now did, knew him for the intelligent, brave, loving man she knew him for than the perception of the vain fool he put on for them. Marguerite marvels that she ever took him for anything else, that she was drawn into the illusion as the rest of England, and France for that matter, was. That she sincerely thought the man she fell in love with was lost.
He makes to get up, searching for his horse, and as he does so he spots Marguerite at the crest of the hill. Their eyes meet, and she feels a thrill run through her, and smiles down at him.
Seizing the reins of his horse, Percy leaps more athletically than she's ever seen into the saddle, galloping up towards her.
"Margot!" He shouts, voice full of excitement, happiness.
Love.