A witness said that onlookers started shouting at the men as they removed the artwork with bolt-cutters.
They said: “He arrived the first time, the bloke, and tried to climb up to the sign and then couldn’t quite knock it, the sign, off its hinges, just with his hand.
“So then he went away and then came back with a pair of bolt cutters and climbed up on the bike.
“He fell off the first time. Then his mate steadied the bike and then he climbed back up again and just bashed the sign off the hinges and then ran off.”
He added: “As soon as it (the art piece) went up online a few people cycled down to it to see it straight away and just sort of hung around.
“When he started trying to knock it off a few people were shouting for him to stop but he just carried on and that’s when he realised he couldn’t get it off with just his hands and had to get some bolt cutters.”
“We await any communication from the local authority as to whether they wish to report a crime.”
Banksy’s works have been removed quickly before.
Valentine’s Day Mascara, a mural weighing 3.8 tonnes, appeared on the side of a house in Margate, Kent, on February 14 this year.
It was taken down a few hours after Banksy had shared a series of photos of it online.
It showed a 1950s’ housewife with a swollen eye and missing tooth, and throwing a man into a chest freezer.
In September the mural was placed in the foyer of The Art of Banksy exhibition in Regent Street, central London, where it can be viewed for free.
The exhibition features pieces including Girl With Balloon, Flower Thrower and Rude Copper and also focuses on Banksy’s Dismaland, The Walled Off Hotel in Bethlehem and recent works acknowledging the ongoing war in Ukraine.
An exhibition also opened at Glasgow’s Gallery of Modern Art (GoMA) this year for a limited run and showcased 25 years of Banksy’s stencil graffiti.
Cut & Run included authentic artefacts, ephemera and the artist’s toilet, as well as a model that explained how the artist shredded Girl With Balloon during an auction at Sotheby’s in London in 2018.
In August, a message on cutandrun.co.uk, said that organisers now “want to take this show on the road but have no idea where to go to next”.
The artist often refers to contemporary issues and in 2020 included messages about the Coronavirus pandemic in his work.
Transport for London (TfL) removed spray paint in a London Underground carriage due to what they called their “strict anti-graffiti policy”.