20.—(1) Where by an agreement made before commencement in relation to extended or revived copyright, and signed by or on behalf of the prospective owner of the copyright, the prospective owner purports to assign the extended or revived copyright (wholly or partially) to another person, then if, on commencement the assignee or another person claiming under him would be entitled as against all other persons to require the copyright to be vested in him, the copyright shall vest in the assignee or his successor in title by virtue of this paragraph.
(2) A licence granted by a prospective owner of extended or revived copyright is binding on every successor in title to his interest (or prospective interest) in the right, except a purchaser in good faith for valuable consideration and without notice (actual or constructive) of the licence or a person deriving title from such a purchaser; and references in Part I of the 1988 Act to doing anything with, or without, the licence of the copyright owner shall be construed accordingly.
(3) In paragraph (2) “prospective owner" includes a person who is prospectively entitled to extended or revived copyright by virtue of such an agreement as is mentioned in paragraph (1).