The FBI paid more than $1.4m to hackers who developed a way to gain access to the iPhone used by one of the San Bernardino attackers, leading the law enforcement agency to drop litigation against Apple intended to force the company to help break into the device.

James Comey, director of the FBI, said on Thursday that the cost was “worth it”, but added that an accommodation needed to be made with Apple and other technology companies in the future, as paying outside technologists to find ways to access highly-encrypted messages on phones used by terrorist suspects was not “scalable.”

Speaking at an Aspen Security Forum event in London on Thursday, Mr Comey said: “We were able to get into the phone because, in an odd way, all the controversy around the litigation stimulated a marketplace around the world?.?.?.?for people trying to figure out if they could they break into Apple 5C running iOS9 — and those details matter because that’s the phone that the terrorists left behind.”