Apps today are known for their ability to provide secure communications. 40 years ago, a man was assigned a secret mission: to create an encryption device that would send intelligence to the top officials. He now speaks out about the assignment for the first-time.
The mission started in a Cheltenham department shop, which was crowded with shoppers. It was 1980, and Mike - his first name is withheld as he remains anonymous - worked in the nearby GCHQ. He bought two standard briefcases.
They were then taken back to the lab, where he started to remove the interiors and stuff them with the most recent technology.
The codename Brahms was given to the result. The briefcase, which was regular in appearance, contained the UK's first portable encrypted communication system that allowed high-ranking officials secure communications.
Secure speech is not a new concept. It was not unusual for leaders of the US or the UK to be able to speak securely during World War Two. A huge machine was needed, which was kept in London's basement of a department store called Selfridges.
However, technology had advanced to the point that a device could now be small enough to be carried and more useful in times of crisis for a larger audience.
The Brahms machine looks just like a regular telephone handset, but has a button at one end. It can be pressed to convert speech into digital ones or zeroes.
The digits were scrambled by a special encryption key, which was kept on paper tape in a briefcase. It is also changed daily. The key was then transmitted to a regular telephone line.
Only another briefcase, with the same key on the paper tape, could decode the message and transform the numbers into a machine-like voice at one end.
Anybody listening in on that phone line will hear a digital hiss.
One person could talk at a given time. It was slow - the average speed of broadband in the UK is 22.4 kilobytes per sec.
One flaw was found. Mike says that the high frequency caused "ladies' voices not to come out very well."
However, Margaret Thatcher, the UK's first female prime Minister was the main customer of the machine.
Mike was assigned a James Bond-style assignment to deliver the Brahms device to a castle in Switzerland, where Mrs Thatcher was holidaying.
Mike was appointed temporary Queen's messenger and given two seats on a flight from Geneva to him and the machine. On his arrival, a brown envelope-carrying man would meet him.
He was offered a gun when he reached the castle. He declined.
The Brahms was used during the 1982 Falklands War. Mrs Thatcher used the Brahms to discuss engagement rules with the Ministry of Defence. This led to the controversial sinking of Argentine Navy Cruiser, the General Belgrano.
Stephanie - Stephanie was again the first name only - worked shifts in a 24-hour GCHQ office that dealt with intelligence.
She recalls that it was a men's toy, and is slightly annoyed that female workers were not allowed to use the Brahms.
The Brahms rang in the early hours of the morning. There were no men working on the shift.
"So, we all looked at one another and said, "Well, there aren’t any men in this office so one of us will have to answer the telephone." "So, we all looked at each other and said, 'Well there aren't any men in the office so one of us is going to have to answer the phone. So I went over and took it."
The other person had just received intelligence that he wanted confirmation of.
She recalls that she knew every piece of information she sent to her chaps was important, and how they reflected it back on TV.
After the invasion, GCHQ needed to quickly grow from only having one or two analysts to produce more than 6,000 intelligence reports.
Brahms meant that they could be called in quickly to help those who needed them.
Instructions are included on the Brahms machine for what to do in case of emergency. Imagine if the machine was being used secretly in a hotel room somewhere overseas and you were worried about the possibility of the device being taken and seized.
Mike is able to recall the options.
Turn off the equipment and then find a way to dispose the key tape. "Destroy it. Burn it. Mike smiles and says that you could eat it in the last instance.
