This Powerline article alludes to a certain heckle, "Who Are You?" directed at UK Labour Party leader Jeremy Corbyn and that Nigel Farage employs to much less success at the EU as sort of a mainstay in the rough and tumble of British politics. Is this a reoccurring joke in British politics, used with some regularity during Parliament sessions? Are there others? To timebox this, say in the last 25 years are still in use.
So reoccurring in this instance means in use by more than one MP. It can't just be some MP's tag line or something.