Despite looking slightly dazed, he is easily identifiable in the photograph because other than the two intended subjects, he is the only member of the crowd looking directly down the lens.

It is unclear whether he is aware of the word emblazoned across the back of the Jeremy Corbyn fan, or what the pair may have been talking about.

The photograph, taken by Lucy Edwards, a London art gallery manager, and posted on Instagram, attracted scores of comments.

Miss Edwards, whose username is laeedwards, said "Couldn't have even planned it (big Dave C in the house, shame he can't read)".

One person said: "Think this could be the best Instagram picture of all time" and another added: "Ha is this really him? He's got a tab on."