...but beware cold-callers selling worthless gems

BEWARE of cold-calling criminals attempting to lure you into bogus diamond investments.

In some cases the stones do not exist, while in others, victims are given gems that are worth far less than promised — if anything at all.

Retired nurse Cynthia Tuck was tricked into transferring £400,000 to fraudsters offering coloured diamonds at a hugely inflated price, according to BBC File On 4. The con started in 2013 when she received a call from Colin Moore who claimed to be working for a firm called World Commodity Trading.

He initially persuaded her to pay £5,000 for a diamond as an investment.

Over the next three years he then convinced Cynthia to part with her lifesavings in exchange for 21 gems.

The firm sent out glossy brochures, had a professional-looking website and also offered seemingly genuine certifications, promising good returns.

When her family managed to track down some of the stones purchased, they discovered they were worth just 10pc of what Cynthia paid for them.

Despite the involvement of five different police forces, no one has been charged.

Other investigations have been more successful. In October last year, three fraudsters were sentenced at Southwark Crown Court for their involvement in a boiler room scam, which works much like a call-centre selling dubious investments. They managed to swindle £415,000 from victims they convinced to invest in worthless coloured diamonds.

Police discovered scripts for employees encouraging them to lure investors in with promised returns of 15-25pc from diamonds — what they described as the ‘investment of the decade’.