Imagine you’re the ruler of France in 1427. Half your kingdom is occupied by the English and their allies. The flower of your nobility has been cut down by English archers with their powerful longbows at the Battle of Agincourt. All seems lost. And then you start to hear stories of some mad peasant girl, Jeanne, who claims heavenly voices have told her she must lead the French army to victory and drive the invaders from the land.

Of course you don’t believe her voices are actually true. Clearly the girl is mad. But the question is could she be useful? Is the story of Jeanne just what you need to stem the tide of pessimism and put heart back into the people and the army?

What other explanation could there possibly be of Joan of Arc’s dramatic rise? At least that’s the idea behind this week’s chapter of A Prize of Sovereigns. Aurthur, the crown prince of a fictionalised France, is persuaded to give a hearing to Mad Marta, the Joan of Arc figure.

In my version of her story, she is less national heroine than a cynically deployed piece on the chessboard to burnish the brand of the royal house.