A man armed with an “offensive weapon” has been arrested in the grounds of Windsor Castle on Christmas Day.
Thames Valley Police said the man, aged 19 and from Southampton, was found within “moments” of entering the grounds at 08:30 GMT.
He has been arrested on suspicion of breach or trespass of a protected site and possession of an offensive weapon.
The force said he did not enter any buildings and members of the Royal Family had been informed.
Thames Valley Police Supt Rebecca Mears, said: “An investigation is ongoing following this incident and we are working with colleagues from the Metropolitan police.
“We do not believe there is a wider danger to the public.”