1For the purposes of this Schedule a qualifying provision for redemption, in relation to a security, is a provision which—
(a)provides for redemption before maturity only at the option of the person holding the security for the time being,
(b)provides for such redemption on one occasion only,
(c)provides for such redemption to occur on the last day of an income period, and
(d)is such that the amount payable on redemption on exercise of the option is fixed (as opposed to variable), is determined at the time the security becomes subject to the provision, and constitutes a deep gain.