Not much a secret, more a 'labour-saving' device. I've picked subject matter i'd already researched and had material about. Another aspect is that what I relate almost writes itself.
We think we know about the 'Conquest' era, After all, at school the teachers whizzed through it at breakneck speed, about as fast as they told us about the 'Anglo-Saxons'. How does it go now, ah: 'William lands on the south coast in 1066, beats Harold and is made king (with a bit of a ruckus outside) at Westminster Abbey at Christmas, 1066.
Really? I've got news for history teachers, it was nearly five years before William could consider himself 'safe', and another sixteen before he thought he could rest easy. He did rest, in a stone tomb.
How does all this write itself? The background is all there, I just have to 'stitch' my story onto it, and the Peterborough Chronicle (E) helps a bit. It provides the bare bones, and the introductions to each book in the RAVENFEAST saga. 1066-71 were VERY busy years.