'They sounded like professionals,' James says of the scammers that stole thousands from him in the blink of an eye.

He should know. The 39-year-old from London whose name has been changed, is a senior professional working in financial markets for a UK bank.

He told This is Money: 'They were posting multiple times per day, market news and updates… the posts they were doing on macroeconomic events were tying in with everything I was reading and everything I knew.

'It sounded and looked very professional,' he added.

When the price of the stock he had been buying, which had been recommended by the scammers, tumbled from £30 to just $1.65, James was shocked.

> Read This is Money's full investigation of this pump and dump scam 

Over the course of six weeks, James had invested £13,000 into a Chinese company, Pheton Holdings, which is listed on the US Nasdaq, via his trading platform of choice - Robinhood.

In the days before the share price crashed, James had withdrawn his investment, having doubled his money. But the temptation proved too great.

He said: 'I saw the price drop by a couple of dollars.' James bought back in on the hopes of making more money when the price corrected.

What James, alongside thousands of other shareholders, didn't know is that Pheton Holdings was being pumped by scammers who already owned stock in the company. 

When the share price fell, it was because the scammers had sold their own significant positions for enormous profits.

In other words, they cash a very large cheque, and the victims lose everything.

Pheton is just one of a number of US penny stocks that scammers have been promoting to investors using deepfake social media adverts showing well-known figures from the financial sector.

James' experience began with an advert on Facebook.

'Your phone picks up the searches you are doing, and the algorithm feeds you particular ads on Facebook,' he said.

'I'm not big on social media and stuff like that, I got taken in quite easily.'

'I normally stay away from these ads, but the new ones are relying on AI, so I saw who I thought was the founder of Revolut talking about how he is setting up a trading fund.'

Initially, James invested just £1,000, but as time progressed, and the share price of Pheton Holdings kept rising, he started getting drawn in.

'The calls that they were making were right. The communication was very professional,' he said.

All the while, the other members of the WhatsApp investing group that he was in were actively discussing the investment.

'It seemed like a very genuine group,' James said, 'and in the evenings they said they were holding sessions to help teach more to novice traders.'

Now, James believes that most of the other members of his investment group were bots or other scammers.

Having spoken to other victims, he says there could be hundreds of WhatsApp groups just like the one he was part of.

Some of these victims lost a lot more money than James.

He said: 'I am doing very well in my career. From a monetary perspective, I'll recover the loss within a couple of months.

'It's fine for me, there are other victims I spoke to that have lost over £250,000, their life savings.'

He added: 'It was more the embarrassment… I work in financial markets, I do this day in day out, and I didn't see through this scam.'

Understandably, victims often don't like speaking about losing money to scammers.

When James told his father about losing money, his dad revealed that around five years ago he had lost £42,000 in an online investment scam, something he had never told James. James' uncle lost over £100,000 in the same scam.

He said: 'It was a pump and dump scam. It was just a different way that they'd approached it - rather than going through WhatsApp and Facebook they set up trading communities online, and of course there was no AI.'

'This stuff's been going around for a long time.'

With the rapid advancement of AI though, these scams are becoming increasingly prevalent, and ever harder to detect.