Berkshire, UK - An armed man has been arrested after breaking into the grounds of Windsor Castle in Berkshire, one of Queen Elizabeth II's main residences, on Christmas Day.

Officers from Thames Valley Police (TVP) and the Metropolitan Police responded to a security breach at around 8:30 AM local time within the grounds of the castle where the Queen is spending Christmas this year.

TVP said a 19-year-old man from Southampton was arrested on suspicion of breach or trespass of a protected site and possession of an offensive weapon.

The man, who is in custody, was not in any buildings on the estate and "security processes were triggered within moments of the man entering the grounds," police said.

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The Queen is spending Christmas Day at Windsor Castle and was expected to have lunch with the Prince of Wales and the Duchess of Cornwall, as well as the Earl and Countess of Wessex.

Charles, Camilla, Edward, and Sophie, along with their children Lady Louise and James, Viscount Severn, attended a church service in St George's Chapel, in the castle grounds, at 10:45 AM on Christmas morning.

TVP Superintendent Rebecca Mears said: "An investigation is ongoing following this incident and we are working with colleagues from the Metropolitan police."

"The man has been arrested on suspicion of breach or trespass of a protected site and possession of an offensive weapon."

"Members of the royal family have been informed about the incident. We do not believe there is a wider danger to the public."