He'd had no plan. He'd just retreated, as people do when they feel under attack, to a more defensible position, i.e. the past, and then something happened which had the same effect on Edward as finding a plesiosaur in his goldfish pond would on a student of ancient reptiles.
He'd stepped out blinking in the sunlight one hot afternoon, after a day spent in the company of departed glory, and had seen the face of the past strolling by, nodding amiably to people.
He hadn't been able to control himself. He'd said, “Hey, you! Who are y-ou?”
The past had said, “Corporal Carrot, sir. Night Watch. Mr d'Eath, isn't it? Can I help you?”
“What? No! No. Be about your b-usiness!”
The past nodded and smiled at him, and strolled on, into the future.
Carrot stopped staring at the wall.
“I have expended three dollars on an iconograph box which, is a thing with a brownei inside that paints pictures of thing's, this is all the Rage these days. Please find enclosed pictures of my room and my freinds in the Watch, Nobby is the one making the Humerous Gesture but he is a Rough Diamond and a good soul deep down.”
He stopped again. Carrot wrote home at least once a week. Dwarfs generally did. Carrot was two metres tall but he'd been brought up as a dwarf, and then further up as a human. Literary endeavour did not come easily to him, but he persevered.
“The weather,” he wrote, very slowly and carefully, “continues Very Hot…”
Edward could not believe it. He checked the records. He double-checked. He asked questions and, because they were innocent enough questions, people gave him answers. And finally he took a holiday in the Ramtops, where careful questioning led him to the dwarf mines around Copperhead, and thence to an otherwise unremarkable glade in a beech wood where, sure enough, a few minutes of patient digging unearthed traces of charcoal.