Illustration by Thomas Henry Nicholson (????-1870) from Cassell's illustrated history of England published circa 1896.
From book text: Henry was actuated by the prospect of getting possession of the whole of Brittany, and affecting to regard Duke Conan as a usurper, confiscated his estate and title of Richmond. Then crossing the Channel with a large army, the king appeared before the walls of Nantes, and compelled the citizens to expel Conan, and to pay allegiance to himself. Henry then garrisoned the town with a body of his troops, and took possession of the rest of the country between the Loire and the Vilaine.
Anticipating the alarm this great increase of his territory would cause in the French court, Henry sent there as ambassador Thomas à Becket, and afterwards followed in person, and a treaty was concluded, by which the French king undertook to maintain his neutrality.