@mikey
It's a supreme example of how advertising works on people. Other than quibbling over the figures, the message itself more or less worked on me. I read it as a pledge, despite it being no such thing.
As observed by Kathyan, above, the Leave campaign is not a political party, yet some part of the brain, on autopilot, read the whole show *as if* it wad an election campaign.
OR: - you could read it that Boris, in his capacity as a member of the Tory party was making promises on behalf of the (at the time) ongoing sitting government. We fill in the blanks about Cameron's defeat leading to his resignation, thus paving the way for Boris/other candidate fulfilling the promise, even before that played out for real.
Anyway, even though debaters, in this thread, have adequately proven that it was never a promise, in the first place, politicians need to become aware that messages they present in campaigns are *received*, by the Great British public, as pledges and promises and failure to deliver is part of why they are no longer trusted, in this day and age.
They need to communicate more clearly, in future. Say the words "this is not a promise" out loud, or print it in big letters under your slogan, if you're not prepared to follow through.