ITV correspondent Jonathan Swain explained: "Everyone's just thankful that he was not armed and that this was not a terror-related incident".
Police have said it is not being treated as terrorist-related.
A palace spokesperson said the Queen was in residence at the time but did not confirm if the monarch had been told about the incident.
"He remains in custody at a central London police station".
A 22-year-old man was arrested on suspicion of trespass at 2am on Wednesday morning.
There were apparently fears the man was attempting a copycat operation to Michael Fagan who famously broke into the Queen's bedroom nearly 37 years ago to the day.
The 22-year-old man is believed to have climbed over the fence from the Buckingham Palace Road side of the building; he was arrested just a few minutes later, according to the BBC.
Cape Town - An intruder wreaked havoc at Buckingham Palace when he breached security in the early hours of the morning and attempted to bang down the palace doors.
Buckingham Palace insiders last night revealed the Queen is to be informed of the incident. "It's very unusual given the infamous Fagan business almost 37 years ago", the source says.
The breach came almost 37 years after Buckingham Palace's most well-known security incident, when 30-year-old Michael Fagan gained access to the queen's bedroom while she was there.
There is a real fear among royal insiders that Wednesday's break-in was a copycat operation of Fagan's.
"How is it possible all these years later that someone can climb the fence and get right inside the grounds without being stopped immediately?"
"We are all relieved that the doors were locked this time and he wasn't able to get inside where the Queen was". What about heat censors and CCTV?