Radiation detectors could be installed across London to protect the capital from a dirty bomb attack, Boris Johnson has said. Supermarket-style self check-out technology could also be used to identify suspicious packages to bolster safety in the city, he suggested.

Mayor of London Boris Johnson in New York's  Time Square, New York

Mayor of London Boris Johnson in Times Square, New York Image by Stefan Rousseau/PA Wire

The proposals have been inspired by the “extraordinary stuff” that protects New York, Mr Johnson said after talks with the US city’s Police Commissioner, Bill Bratton. “I was thinking should we have those kinds of systems?”

Mr Bratton gave the London Mayor a tour of New York City’s Police Department domain awareness system, which brings together radiation detection, 8,000 surveillance cameras and a licence plate recognition system.

Geiger counter-style devices are spread across buildings in the city as well as being carried by police officers and installed in helicopters.

Mr Johnson said: “You can tell automatically here whether a bag has been left in the wrong place in a suspicious way based on the kind of technology that we have, I thought, from supermarket check-outs when it says unexpected item … when you try to automatically buy something from Tesco and it says ‘Unexpected item in baggage area’. That was clearly what’s working very well here and I think we need consider all those kinds of things in London.”

Mr Johnson said he would talk to London police chief Sir Bernard Hogan-Howe to assess the need for such a move.

“What we need to do is to get a better understanding of the risks versus the investment,” he added.

The visit comes as new crime figures show that both cities are making significant strides in the battle to tackle mobile phone theft.

Mr Johnson and the Commissioner were leading figures in an international coalition to the problem through the Secure Our Smartphones initiative.

In London, the number of smartphone thefts has dropped by more than 40% in the year ending October 2014 – a reduction of 20,000. In New York, police recorded a 16% drop in mobile phone robberies and a 25% fall in iPhone thefts between January 2013 and December last year.

Mr Bratton said: “We have very close relationships with our colleagues in the Metropolitan Police in London.”

He added: “Crime and terrorism often ignore geographical boundaries and jurisdictions. Effectively combating these common problems requires seamless collaboration among law enforcement on a global level.

“The NYPD has established strong ties with our London partners in sharing investigative strategies, intelligence and technological approaches to the on-going threats that face both of our cities.”

(Press Association)