We have all done it – opened an e-mail from the supposed crown prince of a small state in Nigeria who is in difficulty and needs our help.

That request for assistance is always financial, as they ask for various sums – some very large – to be forwarded.

There is always an accompanying offer of even larger sums in return. And that, of course, requires bank details.

In the days when we were unaccustomed to such demands, some people responded, keen to help. They lived to regret their actions, never hearing from the ‘prince’ again, and losing substantial sums of their money.

Although, thanks to spam filter systems, they don’t arrive as frequently as they did in the past, scams like this still reach our e-mail inboxes. You would thing we had all learned from past mistakes and widespread publicity to steer clear – but we haven’t.

Across the UK, people still fall for them. “Such ‘online phishing’ scams are by far the most common,” explains David Lodge, divisional manager of West Yorkshire Trading Standards Service. “They are easy to create, can be made to look official and can reach a great many people very quickly.”

Research by the Office of Fair Trading reveals that almost half of the UK population has been targeted by a scam.

Another common scam – which targets people both via e-mail or through the post – singles people out as winners of large sums of cash in prize draws.

Victims include, in particular, the elderly and vulnerable, but anyone can fall for them. Says David: “People are a bit more sceptical nowadays, but these are often so convincing that people think there is a chance that it may be genuine.”

The OFT found that every year more than three million adults – one on 15 of us – fall victim to a scam. Many more go unreported. “Victims often feel foolish, so don’t complain,” says David.

People should treat deceptive, unsolicited mailings with great caution, he stresses. “If someone replies positively, they are repeatedly victimised.”

These names and e-mail addresses are placed on what is unofficially known as the ‘suckers’ list’.

“They are seen as a soft touch - an easy target,” says David. “Their details are sold on, passed round, and they are bombarded with mail. We have been to people’s homes in West Yorkshire who have got sacks full of these things.

“I recall one elderly man who suspected it was a scam, but also thought there was a chance it might not be – he could not help himself.”

Often, claiming the ‘prize’ demands calling a premium-rate phone line or sending money through the post.

“More often than not, those who respond get nothing back, but sometimes they may get a prize, like a cheap travel alarm clock that is worth far less than you have sent.”

Last year the consumer watchdog Consumer Direct Yorkshire and Humber, received more than 1,500 scam-related complaints from householders, including complaints surrounding fake lotteries, prize draws and chain letters.

“When we investigate, we find that, often, they are run from mailbox accommodation, and when we have gone in we have found sackloads of post. We have intercepted money sent to them, so it does not always get into the hands of the perpetrators.”

Scammers also target schools and local authorities – earlier this year Bradford schools and Council departments were warned to be vigilant after a series of scams reported across West Yorkshire involving phone calls to schools purporting to be from the Council advising that electrical testing is due.

An engineer carries out the testing, and the school is subsequently invoiced. Schools have also reported being offered free trials on a training materials website, but not being told about cancellation periods. Incidents surrounding the placing of recruitment advertisements have also been reported.

And wannabe young models have fallen victim to scams after paying up-front fees at mass ‘casting’ sessions at hotels, only to be disappointed when the anticipated work does not materialise and they are left with poor-quality photographs.

David also warns of one-day sales, which hit town centres during summer. “Typically they set up in unoccupied shops, or sometimes hotels, and people are invited in to take part in an auction, usually selling items such as mobile phones or digital cameras,” he says. “They create a frenzy-like atmosphere and make their ‘knock-down’ prices seem a good deal, but often their high-end products are cheap imitation or rubbish.”

Bradford councillor Valerie Slater, chairman of the Trading Standards Committee, says: “Some of these scammers use very sophisticated techniques which makes them difficult for people to spot. You have to be able to look at them with general cynicism.”