Becoming suspicious, Mrs Campbell challenged the man and asked whether he really was from Nationwide. In response, he told her details of her address and recent transactions – all of which were correct.

She said: “He said, ‘are you sure you have not made a payment of £1,500 to Western Union?’

“And I said, ‘I have not’. And he said, ‘OK, well we think your account has been compromised. I now need to help you make the account secure’.”

The man ended the call and rang back via WhatsApp, asking Mrs Campbell if she was happy to continue.

“Reluctantly, feeling a little sick, I have to say, because I wasn’t absolutely sure, but I said OK,” she said.

“He then instructed me to press a few buttons on my phone.”

These instructions, apparently so he could “guide” her through making her accounts safe, actually led Mrs Campbell to share her screen with the man, which is a function WhatsApp introduced for its calls last year.

This allowed him to see what was on her phone, including that she had other accounts, with Lloyds and Wise – a money services provider that specialises in international cash transfers.

For the next 90 minutes, the man instructed Mrs Campbell to shuffle different sums of money between these accounts – and also into a separate Western Union account – watching the transactions go through using screen share, all under the guise of helping her.

“All the while he’s saying to me, ‘we are managing to recover the money, but we’ve got to act fast because it’s going out fast’,” she said.

“So I’m seeing them coming in thinking, ‘well the money’s being recovered’, but you know, stupid me, didn’t realise that he was shuffling it all into my Wise account.”

At one point, he persuaded her to take out a £25,000 loan, apparently to “block” another loan he claimed had been taken out.

Mrs Campbell said: “If that one instruction had come in isolation, I would have said… ‘what planet do you think I live on?’

“But because I’d been groomed and everything was making me feel more and more fearful and more and more insecure, you get swept along by the scammers insistence of acting now.”