There have been various changes to royal security since the 9/11 terrorist attacks prompted a strengthening of procedures at high-profile locations.
Security at Buckingham Palace has been strengthened
At Buckingham Palace, new high-quality CCTV cameras and alarms were installed and armed officers were increased.
But there have been two high-profile breaches since, prompting the creation of a new royal security co-ordinator.
In 2003, a comedian gatecrashed Prince William's 21st party at Windsor Castle and a reporter got a job as a footman.
Twenty eight changes were recommended after Aaron Barschak mingled with guests at the party in June 2003.
Police were criticised for a "series of errors" and a subsequent security review largely focused on the way royal events were planned.
Mr Barschak's stunt prompted a review of security at Windsor Castle
But its recommendations included changes to police control room procedures, better communication between agencies and regular checks of alarms and CCTV cameras.
A new law to make trespassing on royal property a specific crime to act as an extra deterrent was also recommended.
And the new post of Palace Director of Security Liaison, taken up by former SAS officer Brigadier Jeffrey Cook in May, was created to provide a critical overview of royal security.
Brigadier Cook reports to the Queen's private secretary and acts as a principal point of contact for all security matters across the Royal Households.
He also liaises with Commander Peter Loughborough, head of the royalty and diplomatic protection group, who monitors security cameras, alarms and police duties at Buckingham Palace.
After the Windsor Castle incident Metropolitan Police Commissioner Sir John Stevens also suggested the SAS could be used to test security at the palaces.
And he said intelligence would be gathered on people obsessed with the royals and publicity seekers.
"These people may present risks and threats and could encourage more sinister actions from others. In a post 9/11 environment no chances can be taken," he said.
But just three months after the incident, Daily Mirror journalist Ryan Parry reported how he got a job as a palace footman using false references.
Another review focused on tightening vetting procedures for staff and job applicants, which may see M15 taking a lead role.
But it also suggested royal security was most at risk from journalists and others who set out to test measures to cause embarrassment.