A military-grade encrypted communication system used by organised criminals trading in drugs and guns was hacked in a four-year investigation involving police teams across the world.

Thousands of officers from the National Crime Agency (NCA), regional crime squads and every force in the UK took part in the massive international sting.

The NCA today confirmed the operation has so far resulted in the arrest of 746 alleged crime bosses and the seizure of 77 firearms, including an AK47 assault rifle, sub machine guns, handguns, four grenades, and over 1,800 rounds of ammunition.

More than two tonnes of Class A and B drugs have also been seized by police, as well as 55 sports cars, 73 luxury watches and over 28 million street Valium pills – a drug that has caused a number of deaths in Scotland.

After four years of work by international teams, French investigators managed to access Encrochat, an encrypted platform used by 60,000 people worldwide, including around 10,000 in the UK, for what law enforcement agencies claim were purely criminal purposes.

The company, which charged £1,500 for a device on a six-month contract, sent out a warning to users in early June to say that its servers had been hacked by a government entity.

This left investigators with a race against time to make the most of the wealth of information available on the platform, targeting ‘Mr and Mrs Bigs’ before they could cover their tracks.

International investigators were also going after the team who ran Encrochat, who they said led ‘luxury lifestyles’, although the technology itself is not illegal.

NCA director of investigations Nikki Holland said the breach was like ‘having an inside person in every top organised crime group in the country’.

She said: ‘This is the biggest and the most significant law enforcement operation of its kind in the UK and it is previously unmatched in terms of its scale.

‘We have dismantled well-established organised crime groups and have already secured evidence to prosecute a significant number of known criminals that have previously remained beyond our reach.’

The NCA said UK law enforcement had dealt with more than 200 threats to life and had ‘undoubtedly’ prevented murders between rival gangs.

Law enforcement have been aware of Encrochat for some years. Drug dealers Andrew Venna and Matthew Cornwall, who operated in Gloucester and Stroud, used the devices before they were jailed in May 2019; as did Mark Fellows and Steven Boyle, who were jailed for life last year for the 2015 gangland killings of John Kinsella and Paul Massey in Liverpool.

After the platform was accessed, investigators were able to monitor thousands of Encrochat handsets and analyse millions of messages to get information on drug dealing, the sale of illegal guns and money laundering.

NCA deputy director Matt Horne said: ‘This is very much about the organised crime gangs that are operating on street corners, on estates and across communities across the entire UK. Trafficking drugs and using serious violence and use of firearms.

‘It hits right at the heart of the most dangerous organised criminals that are actually on the streets of the UK, that we need to target, and cause real problems for our communities.

‘I assess this is the largest-ever disruptive impact against organised crime gangs operating at a high level involved in drugs importation, in drug trafficking, firearms importation/trafficking, and money laundering that impacts on the UK.’