Detectives also found heroin and cocaine, evidence linked to child sex abuse and forged passports.
The Met Police believe criminals used the centres in Park Lane, Hampstead and Edgware to store criminal assets.
Armed police continue to guard the buildings as specialist officers search the 7,000 safety deposit boxes.
So far only a third of the boxes have been opened and the finds have also included a firearm, counterfeit currency, several works of Renaissance art and a substantial amount of high value jewellery.
Speaking after the raids Commander Allan Gibson said: "Search teams have been working around the clock to open all the boxes at the location and are progressing well, although we are likely to remain at the locations for some time yet. BBC NEWS
Huh? ... Wikipedia:
A safe deposit box (sometimes incorrectly called a safety deposit box) is a type of safe usually located in groups inside a bank vault or in the back of a bank or post office. It usually holds things such as valuable gemstones, precious metals, currency, or important documents such as wills or property deeds that a person might feel afraid to leave at home due to fear of theft, fire, flood, tampering or other reasons. In the typical arrangement, a renter pays the bank a fee for the use of the box, which can be opened only with production of the assigned key, the bank's guard key, the proper signature, or perhaps a code of some sort. Additionally, some banks are using biometric dual control security to complement the already increased security procedures.