Some have supposed this privity to be tenure; some, an interest of the covenantee in the land of the covenantor; and so on.
Hence the plaintiff must always be privy in estate with the covenantee.
The assign, as in warranty, came in under the old covenant with the first covenantee, not by any new right of his own.
If the covenant was to be approached from the side of contract, the heir was party to it as representing the covenantee.
When such a covenant is made, the legal estate in the land passes at once to the covenantee under the statute.