This section is from the book "Real Property, An Introductory Explanation Of The Law Relating To Land", by Alfred F Topham. Also available from Amazon: The New Law Of Property.
When land is granted "to A in tail" (a), or "to A and the heirs of his body," A becomes a tenant in tail, and the land will go to the issue of A after his death.
A's estate is called an "estate tail," and is an estate less than the fee simple, because, if at any time there should be no "heirs of the body" (i.e. issue) of A, his estate will cease. Therefore if X, a tenant in fee simple, grants lands "to A and the heirs of his body," the residue of the fee simple remains in X, and if A's issue should fail the fee simple will go back or revert to X.
The persons interested in the land after such a gift are therefore
(i.) A who can enjoy it for life.
(ii.) A's "children to whom it is given after his death.
(iii.) X or his heirs, who are to take if A's issue should fail, and who are called the reversioners or remaindermen.
Such is the effect of an estate tail at the present day, subject, however, to a right, which is at first sight somewhat extraordinary, namely, the right of A at any time to destroy the rights of all other persons interested in the land, and to give himself the fee simple.
This peculiar right is the result of the history of the law as to estates tail and cannot be properly understood without some knowledge of the curious procedure of the early law which is now obsolete
(a) These words were authorised by the Conveyancing Act, 1881, 44 & 45 Vict. c. 41. s. 51.