He has repeatedly angered Londoners with comments about their city, including remarks at a National Rifle Association meeting in May in which he claimed that London has strict gun laws but has such a bad knife problem that a hospital in the city looks like a "military war-zone hospital".

"Yes, that's right, they don't have guns," he said. "They have knives, and instead there's blood all over the floors of this hospital."

The activists who planned the blimp stunt, known as "Trump Baby", raised more than $US20,000 ($26,000) through an online crowdfunding campaign. About 10,000 people also signed a petition asking for permission to fly the massive balloon. The campaign asked donors to "make our six meter high orange, inflatable baby with a malevolent face and tiny hands fly over central London during Trump's U.K. visit".

After Trump's visit was announced in April, British Foreign Secretary Boris Johnson tweeted that he was looking forward "to seeing our closest ally and friend on the GREATest visit ever".

Now it looks likely that the visit will include an appearance by the blimp, which activists hope will take to the skies for two hours on July 13, coinciding with a "Stop Trump" march planned for the same time.

The creators of the blimp did not immediately respond to requests for comment.

The Washington Post