"The thing I most mislike is that I can't really imagine who it would be. There are any number of people with magical abilities, but none of them seem likely to trifle with Galahad." Janet, for example, he can see being petty, but at the same time there's no reason she should care about Galahad at all (and to be honest if Lan Wangji brought her up he'd probably argue her case). Nightingale similarly has no reason to be interested in Galahad. Crowley or Aziraphale could, theoretically, but both of them are probably thrilled not to think about him ever again.