I have to admit, my mind went blank. It's easy enough to come up with idioms swiped from literature, notably Shakespeare, but history? Most English idioms seem to come from common experiences, crafts and professions, the natural world, and so on. They don't tend to involve famous people or events - or, if they do, they don't stretch beyond a single word (Canutian, anyone?). The best I've come up with so far is "met his Waterloo".
There are some from the classical world - which stands to Britain much as classical China to Japan: "cut the Gordian knot", "Caesar's wife", or even "a cobbler should stick to his last". I could probably think of a few more, but it's still surprisingly thin pickings.
It's not that my mind is badly stocked with interesting facts and anecdotes (many of questionable veracity) about British and classical history, but that they've somehow failed to morph into idioms. We know about Alfred and the cakes, for example, or Robert the Bruce and the spider, but there isn't any common idiom derived from either encounter that might be muttered by people in similar circumstances.
Is there a rich vein of such sayings that has somehow slipped my mind? I would of course be happy to hear suggested examples!