This Part of this Act applies in relation to a farm business tenancy (notwithstanding any agreement to the contrary) unless the tenancy is created by an instrument which—
expressly states that the rent is not to be reviewed during the tenancy, ...
provides that the rent is to be varied, at a specified time or times during the tenancy—
by or to a specified amount, or
in accordance with a specified formula which does not preclude a reduction and which does not require or permit the exercise by any person of any judgment or discretion in relation to the determination of the rent of the holding,
but otherwise is to remain fixed, or
does not contain any provision which precludes a reduction in the rent during the tenancy, and—
expressly states that this Part of this Act does not apply, or
makes provision for the reference of rent reviews to an independent expert whose decision is final.