It's not the first time this has happened - in fact, the defacing of Banksy's artwork is so prolific and normalised that it has its own Wikipedia page, which lists some 50 artworks moved or erased.

Last week, in the wake of the UK riots, the street artist undertook a nine-day painting spree, with exotic animals popping up all over London.

The artworks included a goat, elephants, monkeys, a wolf, pelicans, a cat, piranhas, and a rhino, culminating in a gorilla at London Zoo.

But at least five in the series were stolen, defaced or moved to a secure place for their own protection, many within hours of their arrival. The rhino artwork now lives behind a plastic screen with security monitoring it.

Jasper Tordoff, a Banksy specialist at My Art Broker, says he has heard Banksy's depiction of a howling wolf on a satellite dish - that was removed by masked men within hours of appearing - is already being hawked between galleries.

"It makes a profound comment on how we can't enjoy these things," he says.

"And I don't know how people sell these things, frankly, because it's illegal and they're dealing in stolen goods."

This has led some critics to question if Banksy's fame now eclipses the political value of his work - after all, what is the point of a street artist whose work can't stay on the street for more than a few hours?

Others have said some of his zoo series seemed rushed, and not quite up to the standards of his previous work, lacking in any real message.

For some, he is one of the 21st century's most significant artists. For others, he is a bit of a nuisance that causes house prices to rise - Zoopla data shows a significant increase in areas where the Bristolian artist has worked.

In the last 30 days, Banksy was mentioned 112,000 times on Instagram, Facebook and Twitter, according to Talkwalker, a tool that monitors social media trends.

Interest peaked on the day a cat silhouette appeared on an empty advertising hoarding in Cricklewood, London.

Of these mentions, 15% were classed as positive, 20% were negative and the rest were neutral.

And while some of the negative tweets focused on anger at people removing his artwork, others criticised the work itself, calling it unoriginal and overrated.

"Trite. Obvious. Art for sixth formers," one post on X read.

"I used to like him and now he's just sad," another response said.

Dr Paul Gough, vice chancellor of Arts University Bournemouth and Banksy expert, says some of the reception to the artist's zoo series was a bit lukewarm.

"Some of the feedback was that the stencils were okay, but they weren't top-notch compared to what I've seen before," he says.

But the more intricate work - the piranhas stencilled on a phone box or the rhino mounting a car - "that was Banksy hefting his muscle and saying, 'hold on, I can paint better than this'", the expert adds.

Mr Tordoff says the latest work was "not the old school Banksy we have seen where he comes out with punchy messages".

"There's nothing too clever or technical about it," he adds.

"Banksy's studio came out and said these were just a bit of fun to lighten the mood."

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For Dr Gough, who authored a book about the artist, the Banksy phenomenon is not quite over yet but it is evolving as the artist ages.

"He's middle-aged now - he's got to find a cause and his work as an artist has to mature and diversify," the expert says.

"He has got to watch he doesn't become a national treasure - David Attenborough by spray can."

Banksy artworks are regularly removed to preserve them from the threat of vandalism - but sometimes it is not done fast enough. For Banksy, this doesn't necessarily matter.

"He knows they're not permanent," says Dr Gough. "But he knows that tens of thousands of images will be catapulted onto the internet.

"He is reconciled to the fact the work will not last, but it lasts through notoriety."

What does upset Banksy, says Dr Gough, is when his artwork is removed and placed in galleries.

In 2021, a mural of a girl hula-hooping with a bicycle tyre was removed from a Nottingham wall by the building's owner and sold to an art gallery for a reported six-figure sum.

"It's like domesticating a wild animal," says Dr Gough. "You are taking something that is of a time and a place and then putting it behind bars."

Mr Tordoff says our reaction to Banksy is a comment on our own desire to "protect, preserve and own these things".

"Banksy knows how the public's going to react to all of his works, and there's this idea that we're part of this pantomime," he adds.

It is said that Pest Control, the company set up by the artist in 2009, does not issue certificates of authentication for his street work in a bid to keep Banksy's work in public view, according to Mr Tordoff.

Sky News went to Pest Control for comment - but the elusive organisation did not reply.

While it might seem like a one-way ticket to millions, a Banksy appearing on the side of your home isn't always a blessing.

Two landlords who awoke to a large herring on the side of their Suffolk house during his 2021 Great British Staycation series were fairly disgruntled.

"I'm not sure Banksy realises the unintended consequences on homeowners," Garry Coutts was reported to have said at the time.

"If we could turn back the clock, we would."

They ended up removing the artwork and planned to sell it.

Banksy ascended through the ranks as an underground graffiti artist in Bristol, but while his work is technically illegal, he has never been prosecuted for vandalism.

In essence, Banksy gets away with what other artists do not. In 2013, graffiti artist Kristian Holmes was jailed for three-and-a-half years after being convicted of 39 incidents of criminal damage when he sprayed the UK's rail network.

"There is a sort of double standard to his work," says Mr Tordoff.

"If you also look at a lot of his messages and his work, it's ironic because his fame is contradictory to some of his earlier messages."

Part of the reason Banksy occupies so much space in the national conversation is the fact that his identity is still unconfirmed, although there is heavy speculation.

Mr Tordoff says: "People fantasise over this mysterious character and remaining mysterious in the 21st century, well that's hardcore."

And that mysterious figure, whether you like it or not, is here to stay.

"In terms of the art market, he's on a pedestal next to some of the greatest artists to have ever lived, which is completely crazy if you think it's an artist from Bristol that was producing graffiti," Mr Tordoff says.

"He has carved out his name in history and these pieces will be traded for hundreds of years down the line."