Sections MAM-2.2 or MAM-2.3 shall not apply in respect of the redemption of units in a collective investment scheme by a trustee or manager under a trust deed relating to that collective investment scheme in accordance with a buy-back covenant contained or deemed to be contained in the trust deed at a price that is required by the trust deed to be calculated, so far as is reasonably practicable, by reference to the underlying value of the assets less: