@ Xantecproduct . You ' re right , it is . The Hogwartslocation staff member delivering the letter would be expected to mention Diagon Alleylocation ( as Dumbledoreperson did ) . Hagridperson neglected to do this by just posting the letter through the letterbox . So really it ' s an oversight on the part of Hagridperson ( although obviously in reality he did take Harryperson to DAlocation in person ) .