The smartly dressed couple who approach me in London’s Fleet Street look distraught.

“Our car’s just been clamped,” says the man in his thirties, wearing a black suit and white shirt. “We can’t get home.”

His partner appears on the verge of tears, shakes her head and complains about the harsh parking restrictions in the capital.

“You couldn’t lend us 13.50 pounds for the train fare back to Enfield? We’ll post it back to you,” she says.

Alarm bells ring as soon as they mention money.

They remind me of the young woman who came up to me outside my house last month, asking for money to pay a locksmith after she left her keys at home.

“I live down the road at number 52,” she said, pointing the wrong way down my road. “My purse is inside and I’ll pay you back once he gets the door open.”

And then there was the other woman who needed money for a taxi to hospital to see her husband who’d just been taken ill.

The wheel-clamp couple start to look less plausible. They keep glancing over their shoulders. Their story is delivered too quickly, too neatly — it sounds over-rehearsed.

When I politely decline to help, the mask slips and they utter a string of expletives before marching off.

A quick Google search reveals that their sob story was one of dozens of “stranger in distress” or “Good Samaritan” scams:

“Help! I’ve been mugged and need the cab fare home”; “I’ve run out of petrol and need 10 pounds; “I need some baby milk and can’t find my purse”.

While not exactly the crime of the century, these scams prey on people’s good nature and make you think twice before helping strangers in genuine need.

It makes you wonder how widespread these petty frauds are. Do they happen in other cities around the world or is London is the capital of scams?

Have you ever fallen victim to a scam?