By lunchtime, the artwork had been covered and fenced off by guards, who also placed CCTV cameras at the site.

Hours later, the mural was covered with two metal barriers, with security officials standing watch. Source: AP / Joanna Chan

The Royal Courts of Justice, which houses the High Court, is a Grade One listed building, meaning it has the highest level of historical protection in England.

“The Royal Courts of Justice is a listed building and HMCTS are obliged to maintain its original character,” HMCTS said in a statement.

The mural was Banksy’s first artwork since May, when he draw an image of a lighthouse on a wall in Marseille, France, accompanied by the stencilled words: I want to be what you saw in me.

Supporters say latest artwork depicts ‘brutality’ of government ban

Supporting or belonging to the organisation now carries penalties of up to 14 years in prison, placing it alongside groups such as al-Qaeda and the self-proclaimed Islamic State.

Human rights groups have criticised the ban as disproportionate, arguing it limits freedom of expression and the right to peaceful protest.

Banksy has a long history of pro-Palestinian artwork, painting several large murals on the West Bank separation barrier in 2005, including the pictured Flying Balloon Girl. Source: Getty / Frédéric Soltan/Corbis

Banksy has previously expressed concern about conditions in Gaza. In 2015 when announcing more street art there, he described it as “the world’s largest open-air prison”, with Israel having largely controlled entry and exit from the Palestinian enclave for years.