London police have dismantled a criminal gang responsible for almost half of all phone thefts in the city in its largest operation targeting stolen phones after discovering a thousand of such devices bound for Hong Kong.

The Metropolitan Police (Met) on Tuesday said that after an almost years-long operation it had arrested at least 17 people involved in a criminal network suspected of having smuggled over 40,000 stolen phones from the United Kingdom to China.

The syndicate was believed to have been responsible for up to 40 per cent of all phones stolen in London, according to the force.

“This is the largest crackdown on mobile phone theft and robbery in the UK in the most extraordinary set of operations of this kind that the Met has ever undertaken,” Commander Andrew Featherstone, the force’s lead for tackling phone theft, said.

The force said it had launched an investigation, dubbed Operation Echosteep, after a box bound for Hong Kong containing about 1,000 iPhones – most of which were found to be stolen – was discovered in a warehouse near Heathrow Airport.

Local media had previously reported that many phones stolen from London could be traced to Hong Kong’s Kwun Tong district as well as nearby cities in mainland China’s Guangdong province where they were sold as used goods.