LONDON — A week before President Trump’s working visit to Britain, the mayor of London has allowed an additional participant in the city’s welcome reception: a giant orange balloon of the president depicted as a baby in a diaper.

The balloon was approved amid “Stop Trump” protests planned for the visit starting on July 12. Activist groups and trade unions organized an online petition calling on the mayor to allow the effigy to be flown over Parliament. It drew over 10,000 signatories.

Mr. Trump’s visit to Britain was originally scheduled to coincide with the opening of the new United States Embassy in January, but it was abruptly canceled with a message on Twitter from the president saying he did not want to inaugurate the building because the Obama administration had paid too much for it.

British and American officials speculated that the real reason Mr. Trump had pulled out of the trip was because of the risk of large-scale protests.