It's by no means unusual for journalists to carry out what is genuinely work in a drinking context - interviews and such carried out in pubs etc. I'd suspect that would have been very much Boris's style. And the same can be true in political circles - beer and sandwiches in negotiations with Trades Unions back in the old days, political shenanigans in the Commons Bars.

In itself the presence of drink doesn't rule out the possibility that people are working. But there's a limit, and it seems clear that this was well and truly crossed on numerous occasions.