It was a disaster for Harry when he was rushed back to Britain after his tour of duty in Afghanistan was leaked. But why was his first press conference suddenly cut short with a cutting motion across the throat?

Prince Harry has never shied away from saying how disappointed he was when he had to leave his frontline military duties in Afghanistan and return to Britain.

In 2007, Harry, an experienced helicopter pilot, had been posted to the British media on duty and agreed a strict 'blackout' on his presence in Afghanistan to help protect his safety.

However, after just four weeks, an obscure Australian magazine, New Idea, published the news on its website, writes royal author Robert Lacey – apparently without knowledge of the blackout or the consequences of the breach.

But when the American investigative site The Drudge Report picked up the news a few weeks later and published it on February 28, 2008, the game was really on the rise.

Harry sits with a group of Gurkha soldiers at an observation post on JTAC Hill

Prince Harry sits among officers and men from the three services plus friends from his own regiment as he awaits his flight back to the UK after serving for ten weeks in Afghanistan before his cover was blown by the foreign press

Prince Harry steps off a plane as he returns from Afghanistan at RAF Brize Norton on March 1, 2008

“When the news broke, Harry was at a remote base near the front lines in Afghanistan,” Lacey writes in his bestseller Battle of Brothers. 'He had to be airlifted straight back to the main British base in the country where he was put on a plane to Britain.'

The news hit him hard, Lacey writes, citing Miguel Head, the Defense Department official who had tried to keep Harry's whereabouts secret. Head would later become the brothers' chief of staff.

“He was actually very upset,” Head said. 'He was really down. I wouldn't describe him as angry – he's much more mature than that… He was just very sad about it.”

Prince Harry had flown back with three seriously injured men – and it had been a sobering experience, Lacy writes.

The Prince was still wearing combat gear covered in sand when he landed and sat down for a press conference.

'It was clear he was exhausted. he hadn't washed in a day and a half and he was clearly very upset as he tried to absorb the reality that, once again, something he really cared about had been ripped away from him.

And after just two or three questions, a surprise intervention followed.

'Prince William suddenly stood up from the back of the room. He had been sitting behind Head and when the man in charge turned to look, he saw the older prince making a cutting motion with his hand across his throat – essentially saying, “This is over.”

Head's explanation was simple.

“It was just a brother realizing that at that moment nothing was more important than his brother's well-being. It also says something about the brothers' bond and their authenticity.

Prince Harry, left, walks with his brother Prince William, right, shortly after returning from active duty in Afghanistan, at Brize Norton air base in Oxfordshire

Both his father, Prince Charles, and brother, Prince William – just visible in the background – were in Brize Norton to meet Harry as he returned from active duty

Prince Harry leaves the press conference with his father and brother by his side

Prince William carried much of Prince Harry's gear as they walked to the car

“They won't pretend to be just to play games or to go along with other people's expectations.”

As for the Australian magazine that accidentally broke the embargo, Head was charitable.

“Poor old new idea,” he said to Lacey. 'This little-known, very friendly magazine has faced the worst criticism – especially in Australia, where the monarchy is very popular.

“They had published the scoop of the century and just didn't realize it.”