Diana Wynne Jones said this quote

If you like, you can all think of it as my gift to you. I never had much else to give. You can get on and play your own lives as you like, while I just keep moving. This story of it all can be another gift. I’ve made an arrangement with Adam. When I’ve finished, which is almost now, I’m going to put the bundle of papers in the garden of the Old Fort, before I move on. Adam’s going to get them and take them to his father. And if you read it and don’t believe it’s real, so much the better. It will make another safeguard against Them.But you wouldn’t believe how lonely you get.