The Californian tourists – aged 21 and 25 – displayed a lack of decorum near the forum as they snuck away from their tour group and began scratching their initials into the Roman amphitheatre with a coin. They inscribed a ‘J’ and an ‘N’ in 8cm-high lettering, and also took a selfie with their handiwork before they were bust by Italian police who looked daggers and Caesared them.

The Colosseum was completed in AD80, and in its heyday hosted around 73,000 spectactors who enjoyed gruesome spectacles including gladiatorial fights to the death and the mass slaughter of thousands of animals. It subsequently fell into disrepair and was at one point quarried for its stone.

The ancient monument nowadays attracts around six million visitors a year and is widely regarded as one of the greatest feats of architecture and engineering in the world. Defacing the walls is strictly forbidden, and the vast majority of visitors abide by the rules. The section vandalised by the two women only dates back to the 1800s – when the pope initiated restoration work – but that is unlikely to serve as an excuse.

The tourists issued a statement to ‘La Stampa’ newspaper in which they said: “We apologise for what we did. We regret it, but we did not imagine it was so serious. We’ll remember for a lifetime.”

They could be paying for a lifetime if the experience of one Russian tourist last November is anything to go by. The 42-year-old was handed a four-month suspended prison sentence and a Coloss-al 20,000-euro fine after he was caught carving a 25cm letter into the amphitheatre. The culprit has yet to the pay the fine due to a lack of funds – we suspect because he’d already treated himself to an over-priced ice cream in the Italian capital.

The Russian was the fifth person to have his collar felt for defacing the Colosseum last year – earlier incidents involved an Australian father-and-son, and Canadian and Brazilian teenagers.