Police officers seized £120,000 of criminal cash during a raid of a home in Ruislip.
The huge find kicked off Met wide Operation Big Wing in Hillingdon, focused on targeting drug crime, theft and knife offences.
A man and a woman were arrested for money laundering after the £120k was found.
Officers are carrying out 40 search warrants at properties across the borough today, Wednesday June 25, as part of the operation, the most Hillingdon Police has ever carried out.
The borough's policing efforts make up a quarter of all raids taking place across London.
Detective Chief Superintendent Nick Downing, borough commander, is passionate about taking the money out of crime.
He said: "This was a fantastic way to start Operation Big Wing with a bang."