Buckingham Palace has been the subject of several security breaches in recent years.
In August 2016, a 22-year-old man was arrested at 4 am after he climbed over a security fence and was being spotted by officers monitoring CCTV.
And in May 2016, 41-year-old Denis Hennessy climbed over barbed wire and roamed freely in the palace grounds for 10 minutes while the Queen, Prince Philip and Prince Andrew were in residence, before the intruder was arrested.
In 2013, a man scaled the fence and was found after 10 pm in one of the State Rooms.
None of the royals were in residence at the time.
