High-value watches, jewellery and two kilos of cocaine seized as part of one of the Met’s largest operations to tackle serious and organised crime were found in specially-built “hides” concealed in vehicles.

Three hides were found in transit vans used by the suspects arrested as part of the operation, which has resulted in the arrests of some of London’s most dangerous criminals and £13 million in cash seized.

One of them was built into the floor of the van’s rear, and opened by remote control. The two others looked like an electrical generator box that you might see in the back of any tradesman’s van, and were covered in tools and other building equipment.

During the investigation, officers discovered the complex method of opening these boxes – they first had to be powered up using an electrical transformer device, and a specially-made key fob was required to engage a hydraulic lock inside the box.

Deputy Assistant Commissioner Graham McNulty said: “Criminals go to great lengths to conceal drugs, weapons and the proceeds of their crimes. Officers regularly encounter hides in vehicles and at properties – some are basic, and some are specially constructed at significant cost to stash away evidence and illegal profits.

“Our officers instinctively look for evidence in places you wouldn’t think to look and have the knowledge and expertise to gain access to even the most sophisticated hides with complex locking mechanisms.

“These people think their wealth is untouchable, and the sole motivation for people involved in serious organised crime is money. That is why, as part of these investigations, we will look closely at their finances and use all the resources and legislation available to us to take everything they have obtained using criminal funds away from them, and bring them to justice.”