alternatehistory.com

(n.b. this is provisional, I'm not sure if this is how Komei would have actually acted.)



Late at night, 10/11 August

A rider enters Edo with the Imperial recommendation to the Shogunate.
Emperor Komei has struggled with his recommendation for many hours, knowing that the weakening of the Shogunate in favour of the Imperial court has been largely driven by Japanese dislike of the Western Powers and their commercial interests in Japan.
In the end, the old Emperor's instruction to his young Shogun is simple and to the point - attack, trusting in Japanese supremacy to win the day.

Shogun Iemochi determines to follow the Emperor's orders to the best of his abilities, as part of his (perhaps overly elaborate) plan to ensure that the supremacy of the Shogunate is retained or at least that a viable partnership is possible. As such he has a messenger inform the impatient British commander in Edo harbour that his consultation with the Emperor has been delayed, but that he will be shortly acting to resolve the situation.
About half an hour later, under cover of night, the Japanese attack begins.

The confused battle in Edo harbour is as strange a blend of old and new as could have been imagined. Bakfu troops with swords and spears move in in dozens of small boats, many of them rowed and lent supporting fire by Japanese gunboats and batteries firing solid shot, while the steam warships Kanrin Maru and Kanko Maru move at full (slow) speed along the row of British ships and archers on their decks launch volleys of flaming arrows.

The boarding parties manage to climb the sides of the Pearl, the corvette surprised by the attack to some extent, but good discipline and work by the experienced small-arms men and marines prevents the ship falling into Japanese hands. The Clio, a similar corvette, loses some of her upperworks to fire arrows before she and Bacchante (Maitland's ship once more fully on top of things) damage the Japanese warships and force them to retire.
By the morning, all four British ships - Pearl, Clio, Bacchante and Chesapeake - are clear of further danger, fires out and surrounded by flotsam.