Yes, held the EAT in Seldon v Clarkson Wright & Jakes, a well known and long-running case.
Mr Seldon, formerly a partner in a firm of solicitors, was compelled to retire at age 65 under the provisions of a partnership deed. He complained of direct discrimination on the grounds of age. The appeal courts held that such discrimination was capable of objective justification, and Lady Hale's judgment in the Supreme Court made it clear that measures which sought to achieve inter-generational fairness or dignity at work might amount to legitimate aims.
The case was remitted to the employment tribunal, which held that a mandatory retirement age of 65 was a proportionate means of achieving the legitimate aims of retention, planning and (with some caveats) collegiality. Whether or not age 65 was proportionate was then appealed to the EAT.
The EAT held that the tribunal was entitled to conclude that 65 was an appropriate age, notwithstanding that the point of retirement could have been set at age 66. The employment tribunal had to balance the discriminatory effect of choosing a particular retirement age against its success in achieving the legitimate aims. That balance would not necessarily show that a particular point/age could be identified as any more or any less appropriate than another particular point/age. On the evidence before it, the employment tribunal was entitled to find that a retirement age of 65 was reasonably necessary to achieve the legitimate aims identified.