Peng Liyuan, China’s first lady, may want to get herself a new phone. The wife of Xi Jinping, the president, was snapped this week in Mexico taking pictures on an iPhone. The couple were on their way to southern California, where Mr Xi is to participate in a US-China summit with Barack Obama.

It turns out that Ms Peng’s photos, or any messages sent on Apple’s network, might have been accessed by the National Security Agency, the US signals intelligence service. While Mr Obama will complain to Mr Xi about China’s cyber hacking, leaked documents suggest the agency has tapped the data of millions of Google, Yahoo and Apple customers.

The NSA, founded by President Harry Truman in 1952, and the sister agency to the UK’s GCHQ, has been barely mentioned as politicians have angrily decried industrial and state surveillance by quasi-official Chinese hackers. But it has long been more powerful and more sophisticated than its rivals, and this week’s revelations render it visible.