PICTURE this. You sit down to enjoy a leisurely lunch at a charming little Italian restaurant by the water.

A waiter comes out with menus and as you’re deciding on what to order he comes back with a platter of fresh oysters. You tell him you didn’t order any oysters but he brushes off your concerns with broken English and endearing smile. What do you do?

Do not accept the oysters, it is a scam — and a very expensive one as these British tourists recently discovered.

A tourist from Birmingham, England, was hit with a whopping $795 (€526) bill in Venice after he and his parents shared a plate of oysters given to them by the restaurant, Trattoria Casanova.

The tourist, who wished to remain anonymous, told The Independent that they did not order the oysters, and questioned it at the time but their concerns were brushed off.

He also claimed that they were then given an extravagant platter of “pescato misto,” which included an impressive array of lobster, scampi and sea bass, when he thought he ordered a grilled fish platter.

“I ordered it by pointing at a picture, which showed only one portion without any name or price on it. The picture was on the first page of the menu,” he told The Independent.

“I have to admit it is my fault that I did not check the price, but I did not expect one and a half lobsters together with other fish that would cost us €300 ($453).”

When the eye-watering bill eventually arrived and he queried it, he was told that this was what they had ordered.

He has now written a letter of complaint to Mayor of Venice, Luigi Brugnaro, saying the restaurant, Trattoria Casanova, took advantage of the fact the family didn’t speak Italian.

“I’m not expecting a refund,” reads his letter.

“But I would like to draw your attention to a kind of behaviour that risks ruining Venice’s reputation. They took advantage of the fact that we didn’t speak Italian.”

And worryingly, this doesn’t appear to be a one-off experience.

Reviews of Trattoria Casanova on TripAdvisor are overwhelmingly negative, with many calling the restaurant a “tourist trap” and 57 per cent of the 547 reviewers rating it as “terrible”.

“The waiters barely spoke English yet understood us well enough to welcome us, offer seats, explain their favourite dishes. No-one explained the hidden charges on how the high cost of our bill was worked out. It was much, much higher than the menu indicated,” one review read.

“I embarrassed my family and caused a fuss! So on top of the cost of fish, we were charged for extras such as bread sticks, a small plate of tiny snacks that we definitely did not order (we wrongly assumed these were complimentary, to nibble before our order arrived).”

Another review warned bluntly that the restaurant will “try to exploit anyone who does not speak Italian, which is over 90 per cent of their customers”.

Diners have also shared photos of their exorbitant receipts, often totalling more than $300.