The iPhone 7 is being turned into a phone capable of safeguarding military-level secrets for the UK armed forces.

Telecoms giant BT is hardening the security of the device to allow UK military personnel to use it to discuss ‘secret’ matters and for storing sensitive data.

Describing the iPhone 7 as the “device of choice” for the UK Ministry of Defence (MoD), Steve Bunn, technical business manager for defence at BT, said the phone will be capable of being switched between different modes, depending on the sensitivity of the call.

“We’ve been working very closely with them to develop what we’ve commonly called a ‘dual-persona device’.

“Essentially [it] means you can have voice at official and at secret.”

BT is also working with the MoD to create “secure storage containers” on the device to hold sensitive data, he said.

Describing the work as “going very well”, he said BT originally began working with an Android device, the Samsung Note 4.

“But as more and more development and testing was done, the security associated with it wasn’t deemed to be sufficient, so that’s why we moved [to iPhone].”

However, beyond security, Derek Stretch, business development director with BT, said the main consideration that edged out the Samsung Note was that the iPhone 7 was already widely deployed within the MoD.

BT officials said they were unable to provide more details on the customized device for security reasons.

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A raft of “secure” phones have been released in recent years, from the $14,800 Solarin smartphone to Boeing’s Black phone it developed for the defence and security industry.

The majority of these phones run hardened versions of Android, a choice the makers say is driven by ease with which they can alter Android’s open-source code.

Across the world, various military and security bodies use GSMK’s CryptoPhones, which run a heavily stripped-down version of Android that has had common smartphone features removed to lower the security risk.

Outside of the realm of Android devices customized for security, however, security experts told TechRepublic’s sister site ZDNet the iPhone remains the best all-round choice.

The Ministry of Defence had not responded to a request for comment at the time of publication.

Update: In a statement issued after this article was published, a BT spokesperson challenged the assertion by Bunn that the MoD had determined the Samsung Note 4’s security to be lacking and said the MoD is still testing various devices for suitability as a ‘dual-persona’ handset.

“We would like to clarify that the MoD has not expressed any views about the suitability of dual-persona technology from specific handset/technology vendors and is prototyping a range of devices.”

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