FROM the moment you enter the lobby of Bristol's City Museum and Art Gallery, you know that Banksy has arrived.

The entrance hall has been taken over by the Portaloo toilets, stacked like Stonehenge, which became iconic symbols of the Glastonbury festival a couple of years ago.

But as you go further into the building, you realise the exhibition, entitled Banksy Versus Bristol Museum, has taken over the entire building.

With 100 works – 78 of which have never before been seen in the UK – this is Banksy's biggest ever British exhibition.

The anonymous Bristol-born artist's new works blend cleverly into the existing collection – a Guantanamo escapee can be seen clinging on to the biplane that has flown over the main hall of the museum for years.

Classical statues line the walls of the main hall – familiar images that have been subverted by the artist.

Michelangelo's David is now wearing a suicide bomber's jacket, and the Venus di Milo now appears as an amputee beggar.

We even have Banksy's own version of The Angel of the North. Only this one is dressed like a "chav" heading out for a night on the town – a smear of lipstick, a punnet of chips and carrying her stilettos, presumably because they're rubbing her toes.

Upstairs, the galleries have become an interesting game – spot the Banksy – as he has hidden away new works among the old.

Often they appear to fit in well with the room – among the religious iconography, for example, he has placed an oil of the Madonna and Child, which may seem conventional at first glance, until you notice that the Holy Mother is listening to her iPod.

The classical fishermen in one painting find themselves being attacked by alien flying saucers – some of which even break out of the frame and fly halfway up the wall.

Another traditional oil painting of a girl with a dog now has a computer error window on it.

Meanwhile, a painting of a lake is askew on another wall, and the water is flowing out together with a rowing boat.

The Flight To Egypt by Claude Derain takes on a new Banksyesque slant – with the Holy family's attention now turning to a billboard for Easyjet flights to Cairo.

This idea of merging Banksy's work with other artists' pieces reaches its zenith in the modern art gallery – where a genuine Damien Hirst painting is in the process of being overpainted by one of Banksy's little rat characters.

Hirst donated the painting – a series of colourful geometric dots – for Banksy to complete.

Rebecca Burton, deputy head of collections and archives for the museum, is bubbling with excitement as she takes a look around the show. "The way he has blended his work into our collection is incredibly exciting," she says.

"He has literally taken over the entire museum. This is a place where he probably came when he was a child growing up in Bristol, so to come in and use the pieces he probably knew back then is a brilliant idea.

"It's like he is taking the Mickey out of us, but in a very affectionate way.

"It has been such an exciting couple of days. We keep finding new Banksys in here ourselves."

The back half of the building is dominated by the ground-floor exhibition of Banksy's captivating animatronic animals.

The lifelike creatures are in a series of cages – a monkey sits in the central cage painting in oils, and breathing and blinking uncannily.

Other cages feature a rabbit who is filing her nails, a fish finger swimming in a fish tank, and a nest where a "mother" CCTV camera is feeding her two young chicks.

Cartoon character Tweety Pie is in another cage – looking aged and sad.

Then there's a series of snake tanks, where the "snakes" upon closer inspection, turn out to be sausages and hot dogs.

The leopard on a branch – which caused uproar when it appeared in the window of a New York pet store last year – dominates the back of the room.

It's only when you walk around to the far side of the cage that you realise it's actually an ingeniously folded leopard skin coat.

Another anteroom features Jerusalem by Tawfiq Salsaa. Carved from native olive trees, this intricate scale model of the city was completed entirely from memory by the Bethlehem craftsman – Israel's security blockade has left him unable to visit the holy city for the past 12 years.

A monumental achievement in itself, the piece was purchased by Banksy and "improved", with the addition of 284 toy soldiers (and one terrorist).

A final ground-floor gallery is devoted entirely to "the art of Banksy". No clever playing with the existing collection here – this is all about the man himself.

As if to hammer home the point that Banksy's work has moved on in the past few years, the centre of the room features a collapsed brick wall covered in graffiti – with a sponge washing it off.

The wall opposite features a classic Banksy-style stencil work, where a graffiti artist is daubing "Workers of the World Unite" on a wall, while a cleaner stands forlornly with a mop and bucket waiting to clean it off.

There are bold statements about the value of art (such as a price tag hanging ironically from one of the paintings), "state oppression" (riot police skip peacefully through a meadow), and there's plenty of poking fun at politicians – including a 9ft by 9ft oil painting of the House of Commons, populated entirely by chimpanzees.

Referring to the piece, Banksy quips: "You paint 100 chimpanzees and they still call you a guerrilla artist."

The most controversial piece in the show is likely to be a large portrait of a Muslim woman in full burka – over which she is wearing a "sexy lady" style apron, and holding a frying pan with a full English breakfast.

The exhibition also features a recreation of the artist's studio – littered with thousands of bits of paper containing ideas for potential pieces.

This piece alone is likely to be pored over by Banksy afficionadoes for hours at a time.