A What-if Moment in Medieval History

I am beginning to feel like the Grim Reaper, for lately all I seem to do is write death scenes. Unlike my other books, of course, which all had such happy-ever-after endings.
Anyway, on May 28, 1265, the Lord Edward outsmarted his cousin Harry de Montfort, which does not seem to have been all that difficult. Edward had been held captive since the battle of Lewes the year before, but he was treated more as a guest than a prisoner or even a hostage, and on this May afternoon, he convinced Harry that it would be fun to hold races. Harry and his knights took turns racing one another, while Edward lamented that his new stallion had gone lame. You can see where this is going, can’t you? A pity Harry couldn’t. When Edward got the signal he’d been awaiting from a nearby hill, he vaulted into the saddle of his “lame” stallion and after a mocking salute to his de Montfort cousin, spurred toward freedom. Of course Harry and the other knights pursued him, but their horses soon shortened stride, no match for Edward’s fresh stallion. Roger de Mortimer and his men then rode out to meet him, and the scene was set for the battle of Evesham in August. This is another What If moment of history. If Simon had entrusted Edward into the custody of his son Guy instead of Harry, he’d not have been able to escape. Why am I so sure? Because when some of Edward’s supporters had tried to free him from Wallingford Castle that past November, Guy had threatened to send him out to them--via a mangonel. And there would have been no Evesham if Edward had remained Simon’s hostage. English history would have taken a dramatic detour—and so would Welsh history.