(2) Where the parties to an employment contract to which this section applies agree in writing, at any time on or after 1 April 1992, to confirm or vary the age specified in the employment contract, the age, as so confirmed or varied, shall have effect notwithstanding section 22.
(4) Where, as at 1 April 1992, the age at which an employer is required to retire, under a term of that employee's employment contract, was specified only in a document that sets out the employer's policy on the retirement ages of the employer's employees or any of them, this section shall not apply in relation to that employee's employment contract.