A Soldier’s Bride by Fenella J Miller

Lord Peregrine Sheldon, Lord Aubrey’s twin, is an intelligence officer for Wellington. When he is reported missing, presumed dead, Beau, The Duke of Silchester, does not believe this dreadful news and decides to go to Spain and find Perry.
Sofia, an English girl living in a Spanish hill village, fights with the partisans, wears a gentleman’s attire and is as far from a society miss as one could hope to find.
Perry is seriously injured in a fall and recovers consciousness to discover he is not only blind, but has no notion who he is, or what he is doing in the foothills of the Spanish mountains. Sofia discovers him and he is taken to her mother’s home in the village to recover.
Inevitably, they fall in love and Perry is finally able to declare his feelings when his memory and sight return. They are from different worlds and both soon regret their marriage. Sofia feels trapped by the conventions and rules of his world and Perry believes his lovely young bride will never settle in England after her wildlife in Spain.
Will their love be enough to overcome the social gulf between them? Can the duke step in and persuade them to stay together?