[Thanks to Rosa Dickinson of St Philips Chambers for preparing this case summary]
The EAT (HHJ Peter Clark) has handed down its decision in Lisboa v Realpubs, in which it held that "less favourable treatment on grounds of sexual orientation" covers any case where sexual orientation, whether of the claimant or a third party, is an effective cause of the detriment suffered. This follows the principle from Showboat Entertainment v Owens 1983 (in the context of race).
The employer was transforming a formerly "gay pub" into a gastropub. While this was in and of itself unobjectionable, the methods of doing so (including asking the claimant to display a board outside saying "this is not a gay club" and asking him to seat customers who did not appear to be gay in prominent positions) amounted to less favourable treatment of gay customers.
Under the principle from Showboat Entertainment, this less favourable treatment of third parties on grounds of their sexual orientation also amounted to less favourable treatment of the claimant on that ground.