It seems that the Chinese have not heard of the IT superstition of never claiming that your computer system is the most secure in the world. Apple made that mistake, but it turned out that any security it had only worked if no-one could be bothered to hack it.

Now China claims it will soon have the world's most secure major computer network, making communications between Beijing and Shanghai impenetrable to hackers. In what amounts to a challenge to the US spooks and 12 year old hackers, they claim that a fibre-optic cable between the two cities will transmit quantum encryption keys that can completely secure government, financial and military information from eavesdroppers.

Prof Pan Jianwei, a quantum physicist at the University of Science and Technology of China (USTC) in Hefei, who is leading the project said that after the Edward Snowden affair that China learnt that it was always being hacked.

"Since most of the products we buy come from foreign companies, we wanted to accelerate our own programme," he added. "This is very urgent because classical encryption was not invented in China, so we want to develop our own technology."

The £60 million cable, which is being funded by the central government and has been supported by the Central Military Commission, will initially mostly be used for money transfers by ICBC, the world's largest bank.

Prof Pan said eventually all communications in China, down to storing photographs on cloud servers, could feature quantum encryption.

"Ten years ago it was not so easy to get sufficient funding to support theoretical research, but since 2006 and 2007 when the economy really went well, they have been putting more money into research and then it really sped up," he said.