What do you think of graffiti? Is it a respectable form of urban art? Or a crime that's blighting our cities? The thing is, graffiti is nothing new. Far from it. The ancient Romans were keen graffitists. And we’ve learned much about them from their carvings on walls and monuments. Declarations of love, political slogans and philosophical statements were popular subjects in those days. But graffiti is even older than the Romans. It actually dates back to 30,000 BC – making it one of the oldest forms of human artistic expression. The earliest examples exist in the form of cave paintings and pictographs and were probably made using tools such as animal bones and pigment. In fact, the only known source of the Safaitic language (an ancient form of Arabic) is from wall drawings. Another example of how graffiti is a link to our past. But things have changed since then. Bones and pigment have been replaced by the spray-can. Many people consider the US (and New York in particular) to be the spiritual home of modern graffiti. There was an explosion of street art in the city in the 1970s, especially in subway stations and on the sides of underground trains. Sometimes whole carriages were covered with graffiti. And it wasn’t simply people scrawling their names (or “tagging” as it’s called) – some were complex and powerful works of art. One of the most famous modern graffiti “artists” is Banksy. He’s from England and operates mainly in Bristol and London, but his fame is global, and his works can be seen anywhere from Los Angeles to Palestine. Indeed, Banksy is now so popular that both Cristina Aguilera and Angelina Jolie are both rumoured to have bought his works. And in 2007, a piece of his (Space Girl & Bird) sold for £288,000. Banksy’s works are often satirical and deal with politics, culture and ethics. One Nation Under CCTV was a comment on Britain’s “Big Brother” society. It appeared on the exterior wall of a building in London, and consists of a small boy painting the words “One Nation Under CCTV” in giant letters. In the bottom left-hand corner of the wall there’s a picture of a security guard with a dog. The work became a landmark in London, attracting visitors from around the world. Ironically, Banksy managed to put it up whilst being watched by real CCTV cameras! In many other places, graffiti is considered a crime. However, Banksy, and thousands of others like him, continue to defy the authorities all over the world. But are they criminals committing acts of vandalism, or artists upholding an ancient and significant tradition? You decide.