The wrong trousers

Lawyers, as we all know, are not only fine, upstanding members of the community, but also big spenders. But that doesn't matter a jot when you want to get into the Dover Street Wine Bar in London – at least not if you've got jeans on.
One partner at a leading regional firm, however, came up with an ingenious way of getting round the dress code on a recent trip to London. After sinking a few ales in a local drinking establishment, the lawyer, with two colleagues, made his way to the bar, only for his friend to be turned away for wearing jeans (this is something of a bizarre rule given today's fashion for dress-down, but there you go). Anyway, our cunning friend thought he could get round the rules by going into the loos, taking off his suit trousers and then handing them to his female colleague to take to their friend, who was waiting outside.
Unfortunately, the pair were caught mid-exchange in the men's loos. The burly security guards didn't think much of their story and ejected them from the establishment for performing indecent acts in a public place. What does a man have to do to get a drink in this crazy town?