Dr. Wilander is the guardian of the Lead Casket [although I don't recall at this point whether he remembers this]. (It's not explicitly stated, but considering what "Faber John" means, his alias is surely a hat-tip to the Norse folk-hero Volundr, known in England as Wayland the Smith.)|
When the four guardians reassemble themselves into Faber John, Dr. Wilander is the one he most obviously resembles, and he continues to occupy Dr. Wilander's rooms at [Seldom End]? (despite Sempitern Walker's assumption that he will want the Annuate Palace back).