Three men were arrested in the Square Mile by City of London Police yesterday on suspicion of running a so-called "boiler room" scam selling wine investments.
Victims were allegedly sold wine by salespeople who cold-called from an address on Fleet Street. They were promised between eight and 40 per cent profit on investments.
Detectives from the fraud team also searched two addresses in Southwark and one in Lewisham.
The losses of those targeted are estimated to run into the millions.
The investigation began following reports made to Action Fraud, the national fraud and cyber reporting service. So far 39 victims have filed reports, but detectives have contacted many who were not aware they had been victims of fraud.
Victims were told the wine was being kept in storage for them, and were pressed to buy more wine to make it more attractive to potential buyers. Many of those affected were elderly, the police said today.
City of London Police detective inspector Andrew Thompson said: “Boiler rooms continue to be a major threat to individuals in this country and statistics show that those who are over 60 are particularly vulnerable to this type of crime."
He added: “I would urge anyone who is cold called and offered investment opportunities to put the phone down and always do your research before making financial decisions."
The arrests were made as part of the City of London Police's Operation Broadway, which targets illegal activity based at some of London's most iconic addresses.
Read more: Cold calls are on the rise