"Ah, I can’t quite remember the in’s and out’s of it, but I’m pretty sure he was in legal trouble - something to do with exploding toilets I think - and he informed on us to get the charges dismissed. Anyway - so he grassed us up, but we carried on obviously. Everyone who wanted to be involved was asked to sign a bit of parchment that was jinxed so that if someone betrayed us, we’d know who - not that we told anyone that though, obviously; Hermione’s idea," he added, and Draco looked quietly impressed, " And then we brought everyone to the Room," he gestured with a sweeping arm to their surroundings, "and came up with our group name. Everything was pretty great for months and months, until Marietta Edgecombe told Umbridge about us - and you can probably remember how that went," Harry said dryly.