Tourists in Rome are often told to beware of self-styled centurions or gladiators who pose for photographs with them in front of the Colosseum and other monuments – and then demand extortionate fees.

Yesterday, however, one “centurion” found himself charged with assault after allegedly punching and kicking four Americans who offered a fee that he found insulting. Two victims ended up in hospital and police arrested the centurion after identifying him from the tourists’ holiday snaps.

Some of the “centurions”, who dress up in crested helmets, sandals, capes and plastic breastplates are licensed by Rome city council. Others, such as the man being held, operate without official approval, despite repeated crackdowns by the authorities.

Jose Nazar, 50, a wine-loving wealthy businessman from Los Angeles, had won a trip to Umbria in a charity auction in California, which included a stay on the estate of a leading wine producer. The group decided to spend a day in Rome on the way.

“We arrived in Rome and thought it was just marvellous,” he told police through an interpreter. “We did the classic tour, we visited St Peter’s – and then we wanted to see the Colosseum. When we saw the centurions we couldn’t resist the temptation of a souvenir photo.” They were approached by one centurion – a “big imposing guy” – and happily posed with him. The smiles faded however when they offered him 4 euros (£2.70p), and disappeared altogether when they said 6 euros was their limit. Unauthorised centurions often charge 20 or 30 euros. Some have been known to offer to take photos with the tourists’ own cameras – and then refuse to return them until they have been paid.

“We didn’t understand what he wanted,” Mr Nazar said. “He became vulgar and aggressive and started insulting us, then pushing and pulling us. We moved away thinking that was the end of it. Instead he came at us and started attacking us savagely with kicks and punches, screaming and shouting. No one came to our aid.”

Mr Nazar told The Times he had a 50-euro note in his pocket “but I wasn’t going to give him that, so I pulled what change I had out of my pocket”. He had added a $2 bill (£1). “But the guy said, ‘We blow our noises with these in Italy’, put it back in my pocket and started hitting me.”

Mr Nazar suffered injuries to his leg and foot and a 40-year-old woman in the party also needed medical treatment.

Police in Rome said that they recently arrested 28 unlicensed fake centurions and charged them with “violating laws banning commercial activity in an archaeological area”. They said that the problem was compounded by turf wars between rival gangs keen to monopolise on the tourist photo scam.

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— The Colosseum is Italy’s most visited archaeological site, attracting 3 million tourists a year

— A spokesman for Rome council said the system of licences was introduced because some unofficial “centurions” were “giving the city a bad name”

— “Real” centurions can be distinguished by their more authentic garb, including metal helmets, breastplates and leather tunics

— The swords, however, are plastic. Four years ago police arrested a “gladiator” who carried a real sword and charged him with possessing anoffensive weapon