Prince Harry was moved under guard to a secure location during a Taliban attack on Camp Bastion, the base where he is deployed in Afghanistan, Britain's defence minister has said.
Two US Marines were killed and unprecedented material damage caused when attackers armed with guns, rockets and suicide vests stormed the NATO base in Helmand province last Friday.
"Additional security arrangements" are in place to protect Britain's third in line to the throne on his second tour of duty in the country, Philip Hammond told BBC's Newsnight on Monday when questioned about the assault.
"Clearly there are fall-back plans and I can't go into the detail of them - but once we knew on Friday night that the perimeter at Bastion had been breached he would have been moved to a secure position under effective guard," he said.
The prince was about two kilometres away with other Apache crew members when the heavily defended NATO base was attacked, but was not in danger, according to Hammond.
He said that while the 28-year-old royal is "no more or less exposed than any other Apache pilot" in combat, he remains under close protection.
"He is serving there as an ordinary officer but clearly there are additional security arrangements in place that recognise that he could be a target himself specifically as a result of who he is," Hammond added.
Although the Taliban have vowed to kill Prince Harry, one of its spokesmen told AFP that Friday's assault "had nothing to do with the prince".
The attack was the first in a wave of violence at the weekend which also saw six NATO soldiers - two of them British - killed in suspected shootings by Afghan police.
The deaths took to 51 the number of Western soldiers killed by their Afghan colleagues since the start of the year, in a growing trend that jeopardises NATO plans to train local forces to take over when they leave.
Earlier Hammond moved to assure British lawmakers that the surge in attacks would not derail Britain's operations in Afghanistan, where some 9500 British troops are deployed.
"Our strategy is clear. We are mentoring and training the Afghan army and police to deliver security to their own people," he told Britain's House of Commons.
"We cannot and we will not allow the process to be derailed," he added.