The arrest of a man at the gates of Buckingham Palace in London on Tuesday evening is not being treated as terror-related, the Metropolitan Police said on Wednesday.

UK Security Minister Tom Tugendhat, meanwhile, stressed that he is “very proud” of the police response to the incident, which came just days before King Charles and Queen Camilla will be departing the palace gates for their grand Coronation ceremony, procession towards Westminster Abbey.

Buckingham Palace said that neither the King nor the Queen were at the palace at the time of the incident.

The suspect, whose actions are being referenced by police sources as an isolated mental health incident, remains under arrest on suspicion of possession of an offensive weapon after he is believed to have hurled shotgun cartridges onto the palace grounds.

A “suspicious bag” in his possession was subjected to a controlled explosion by specialist Met Police officers as a precautionary measure.

The government is mounting "a huge security operation" ahead of the Coronation, and Tugendhat said that “intelligence services, the police and others have been working on this extremely effectively for months”.

"As you saw last night, the police and security services are absolutely ready to intervene when necessary," he told the BBC.

“Officers worked immediately to detain the man, and he has been taken into police custody. There have been no reports of any shots fired or any injuries to officers or members of the public,” said Joseph McDonald, Chief Superintendent of the Met Police.

The police force said roads that were cordoned off and closed in the wake of the incident have since reopened.

The Met Police is undertaking one of its largest policing operations in history as it prepares for the historic Coronation procession that will leave the palace grounds and head towards the Abbey on Saturday morning and make a return journey in the afternoon.

An estimated 7,000 military personnel have been training for the grand spectacle involving officers on horseback and foot marching with the regal procession through the streets of London.

“The Coronation Service itself will last for two hours and remain a sacred Anglican service, but there will also be representation from other faiths to reflect the diversity of modern Britain,” said Duke of Norfolk Edward Fitzalan-Howard, the Earl Marshal – whose family has had the responsibility to deliver State Occasions such as the Coronation since the 15th century.

“It was agreed in the early stages of planning that it would not be possible to close the Abbey for five months to build the extra seating to allow 8,000 people to attend, as had been the case for the Coronation of the late Queen Elizabeth, due to cost and challenges of installing new seating within this ancient building, and the impact it would have on Abbey’s regular programme, he said.

"The invitations this time have been sent to approximately 2,300 people, and the composition will reflect a broad cross-section of national and international guests,” he added.

Approximately 100 Heads of State from around the world are expected to attend, together with royal family members, representatives of the Realms and the Commonwealth and the government, the House of Lords and Commons, local heroes and British Empire medallists and selected individuals who have contributed to society.

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