British Liberators in the Age of Napoleon: Volunteering under the Spanish Flag in the Peninsular War

From the Publishers:
 
This book unveils the role of a hitherto unrecognized group of men who, long before the International Brigades made its name in the Spanish Civil War, also found reasons to fight under the Spanish flag. Their enemy was not fascism, but what could be at times an equally overbearing ideology: Napoleon's imperialism.
Although small in number, British volunteers played a surprisingly influential role in the conduct of war operations, in politics, gender and social equality, in cultural life both in Britain and Spain and even in relation to emancipation movements in Latin America. Some became prisoners of war while a few served with guerrilla forces.