Marshall Entered into an Oral Contract with His Brother Harry

Marshall entered into an oral contract with his brother Harry to transfer his beneficial interest in a trust of a collection of Picasso paintings to Harry in exchange for a payment of £800,000. The payment was duly made. Marshall has:

A) Transferred part of his interest in the shares to Harry, but must complete the transaction in writing to transfer the remainder of his beneficial interest.
B) Validly transferred his beneficial interest in the shares to Harry.
C) Failed to transfer any of his beneficial interest to Harry, as he has only entered into an oral agreement.
D) Can be forced to transfer his beneficial interest, as Harry has paid under the oral contract.