22.—(1) Any document permitted or required by this Act to be served on a rent-owner is duly served on him if it is served—
(a)on any person who acts as agent for the rent-owner in respect of the land in question; or
(b)on the person who last demanded or received ground rent for the land.
(2) Any document permitted or required by this Act to be served on a rent-owner or a rent-payer may, where joint tenants or tenants in common are the rent-owners or rent-payers of any ground rent, be served on any one of them in respect of that rent, and such service shall be taken to be service on both or all of them.
(3) Where the estate of a rent-owner is subject to a mortgage and either the mortgagee is in possession or a receiver is in receipt of the rents and profits, any document required or permitted by this Act to be served on the rent-owner may, instead, be served on the mortgagee or the receiver, as the case may be.