Simultaneous raids in four countries across Europe in the early hours of this morning will "severely disrupt" the drug trade, officers hope.
The National Crime Agency (NCA) in London coordinated with colleagues in South Africa, Bulgaria and Spain to targeted 25 addresses at four o'clock this morning.
Eight properties were targeted in London and eight people were arrested and are now being questioned at police stations in the capital.
They also raided safe deposits boxes in Mayfair and St Johns Wood, collecting a total of £500,000 in cash and diamonds valued at £100,000 and designer watches.
The NCA believe these are assets bought with money laundered after "tonnes of heroin, cocaine and cannabis" were sold on the streets of the UK.
They allege that the individuals arrested are involved in turning the money raised through drugs into apparently legitimate assets, such as diamonds and property.
The hope is that these raids will "severely disrupt" the drugs supply chain.
During a raid on one of the London properties officers used a cash-sniffing dog to help identify a stash of money.
A total of 250 officers were involved in the raids across all four countries.