Boris Johnson, a former London mayor, has been one of the figureheads of the movement to take Britain out of the EU and has pledged to complete the schism by the end of October.
Inspired by the orange blimp of a baby Donald Trump that mocked the U.S. President during his visit to London last month, the balloon featured Johnson in a t-shirt emblazoned with a red bus and the figure 350 million pounds, referring to his promise of clawing back cash from Brussels to spend on Britain's state health service instead.
Prime Minister Theresa May announced her resignation two months ago after failing to win parliamentary approval for the exit deal she had negotiated with Brussels and her successor will be announced next week.
Johnson, who is widely expected to replace her, has pledged to leave the EU with or without a transition deal on Oct. 31.
Brexit without a divorce deal would abruptly wrench the world's fifth largest economy away from the bloc. Critics say this would undermine global growth, buffet financial markets and weaken London's position as the pre-eminent international financial center.