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.
Any joint tenant may sever the joint tenancy, i.e. turn it into a tenancy in common.
He may do this by (i.) an agreement to sever, (ii.) by a sale or transfer of his share to another person, or (iii.) by a mere agreement to sell or transfer (b).
(b) Brown v. Raindle (1796), 3 Ves. Jun. 256; and Be Hewett (1894), 1 Ch. 362.
But a declaration by one joint tenant that the tenancy should be severed, is not sufficient unless it amounts to an agreement (c).
A mere intention to sever is not sufficient (d).
If one joint tenant conveys his share to another person, the grantee becomes a tenant in common with the others.
Thus, A, B, and C are joint tenants; if A sells his share to D, D becomes a tenant in common with B and C; but B and C remain joint tenants as between themselves.
If D dies, his share goes to his heir; but if B dies, his share goes to C.
A joint tenancy cannot be severed by will (d).