A landlord has let a first floor flat to a tenant under an assured shorthold tenancy (AST) in 2014 (A). The ground floor is also owned by the landlord and is let to the landlord’s son (B). Around six months ago, with the full approval of A, the internal staircase was removed and an external staircase constructed outside, giving A his own dedicated access. Both (now completely separate) properties still carry the same address (say, No 4, X Street—not split into 4a and 4b). The first floor property has no letterbox and so post is delivered through the letterbox of the ground floor flat, and B takes post addressed to A up the staircase and leaves it through A’s door, for which B has a key. The AST provides for service of notices by post. Would delivery by this method constitute good service?