Two men have been arrested by police after a break-in at Buckingham Palace earlier in the week.
It's one of the most serious security breaches at the Queen's London residence in 30 years.
Former Protection Officer for Princess Diana, Ken Wharf:
(SOUNDBITE) (English) ROYAL SECURITY EXPERT, FORMER PROTECTION OFFICER TO PRINCESS DIANA, KEN WHARF, SAYING:
"It does happen and it will happen again simply because you cannot give anything 100 percent security when you allow access so close by the general public which... And this is a global tourist spot, one of the most visited places in the world."
Some visitors found the incident worrying.
SOUNDBITE (English) VISITORS SAYING:
"When you just go to visit they haven't... they have so many security procedures there already, so for someone to get in when it's closed and there's meant to be a lot of security stuff going on, it is quite scary, because you think, where else could they have got into ? Especially when she is home, they might be able to get in again."
Officials say one man scaled a fence to gain entry at night to an area normally open to the public during the day.
A second man, suspected of conspiring in the burglary, was arrested outside the palace.
Both have been released on bail, and an investigation is underway.
Two men arrested after palace break-in (1:11)
Police say two men were arrested in connection to a reported break-in at Buckingham Palace. Gavino Garay reports. ( Transcript )