A controlled explosion was performed outside Buckingham Palace on Tuesday after a man was arrested on suspicion of possessing a weapon, the Metropolitan Police said.
He was held at about 7pm after he approached the gates and threw several items, including what was believed to be shotgun cartridges, on to palace grounds.
Deputy Assistant Commissioner Ade Adelekan said the man had approached officers asking to see a soldier at about 7.15pm on Tuesday.
When the officers said that was not possible, the man allegedly began throwing shotgun cartridges over the gates of Buckingham Palace.
He was searched and allegedly found to be in possession of a lock knife, and was arrested on suspicion of possession of a knife and ammunition.
During the arrest, the man told officers that they should handle his rucksack with care, which led to a controlled explosion being carried out on the bag.
Mr Adelekan said the suspect was detained within seconds and arrested within five minutes.
He said he had no knowledge of reports that the man had been shouting that he wanted to kill the king before he was arrested.
The suspect has undergone a mental health assessment and has been deemed fit to be interviewed, police said on Wednesday.
Neither King Charles nor Queen Consort Camilla were at Buckingham Palace at the time of the arrest.
But the monarch had hosted Australian Prime Minister Anthony Albanese during an audience at the palace earlier on Tuesday.
The royal residence was cordoned off after the incident.
The UK prepares for the coronation of King Charles III — in pictures
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Royal enthusiasts at their impromptu campsite on The Mall in London, where they await the May 6 coronation procession of King Charles III. Getty -
Police officers patrol near Westminster Abbey as security is heightened for the coronation. AFP -
A telephone box in the village of Compton, Surrey, decorated with the ears, nose and crown of King Charles. AFP -
A royal fan takes a break after booking his spot on the coronation route in London. AP -
Town crier Tony Appleton takes the train into central London. AFP -
The drum major's state coat, adorned with the new CR III cypher, to be worn during the coronation. AFP -
Decorations are put up outside Number 10 Downing Street in London. AP -
A royal fan gets into the spirit of the coronation on the Mall outside Buckingham Palace. Reuters -
Yeoman of the Guard, the British sovereign's bodyguards, prepare to board a bus in London. Getty -
The UK's military held a full dress rehearsal for the coronation ceremony of King Charles III on Tuesday night. Reuters -
A royal fan sleeps at The Mall outside Buckingham Palace as the countdown to the coronation continues. Reuters -
Big Ben, in central London, is lit up during a rehearsal for the ceremony. PA -
An art installation in London depicts St Edward's Crown. AP -
Madame Tussauds in Sydney, Australia, unveils a waxwork figure of King Charles, alongside figures of Prince William and his wife Kate. Reuters -
Royalists have slept out on The Mall in London for days for the best view of the ceremony. EPA -
A knitted coronation-themed postbox topper in Isleworth, London. AP -
Tailor William Skinner with a ceremonial uniform on Savile Row, London, before the coronation of King Charles III and Queen Consort Camilla, on May 6. Reuters -
Caroline de Guitaut, deputy surveyor of the King's Works of Art, adjusts the imperial mantle, a part of the coronation vestments, in the Throne Room at Buckingham Palace. AFP -
A banner celebrating the coronation at Kings Cross Station in London. AP -
Upholsterer Beatrice Ekwalla works on restoring a throne chair for the coronation at the Marlborough House workshops in London. AFP -
Royal fan Margaret Tyler poses for a portrait in the living room of her home in north London. EPA -
Parliament Speaker Sir Lindsay Hoyle with the Speaker's State Coach. PA -
Violinist Adrianna Forbes-Dorant, 17, takes part in a rehearsal with the Brixton Chamber Orchestra for coronation performances in London. AP -
British Army soldiers rehearse at RAF Odiham for a coronation parade. Getty -
Shoppers browse souvenirs for the coronation of King Charles III outside the Houses of Parliament in London. Reuters -
Temporary stands are constructed on The Mall outside Buckingham Palace, central London. PA -
Members of the military pass by Westminster Abbey in central London during a night-time rehearsal for the coronation. AP -
Britain's Prince Edward, the Duke of Edinburgh, attends a Coronation Big Lunch at Westminster Abbey. Reuters -
The London Scottish Band in Burlington Arcade, London, at an unveiling of a celebratory installation to mark the coronation. PA -
A crown is placed on top of a flagpole on The Mall in London. Getty Images -
The official 'Crowning of the King' souvenir programme sits on a shop shelf in central London. AFP -
Workers prepare the balcony of Buckingham Palace for the big event. AFP -
Ardent monarchist Anita Atkinson sits among her 13,283 pieces of royal memorabilia at her Weardale farm near Bishop Auckland. AFP -
Members of the Household Cavalry take part in a rehearsal for the coronation at Buckingham Palace. Getty Images -
King Charles and Queen Consort Camilla will travel to the coronation in the modern Diamond Jubilee State Coach and return in the Gold State Coach, pictured. PA -
A potter works on chinaware produced for the coronation at a factory in Stoke-on-Trent. AFP -
The Coronation Chair, also known as St Edward's Chair or King Edward's Chair, at Westminster Abbey in London. AFP -
King Charles is presented with the first struck £5 coronation coin by Royal Mint chief executive Anne Jessopp and director Rebecca Morgan at Windsor Castle. Reuters -
The first struck £5 coronation coin. Reuters -
A member of staff at Fudge Kitchen puts up bunting in Windsor. PA -
A crown made by British milliner Justin Smith, created using 319 Scrabble tiles to mark the board game's 75th anniversary and the coronation. PA -
People browse a souvenir kiosk in London. Reuters -
The new commemorative 50p coin, part of the coronation coin collection. PA
It is understood the incident is being treated as an isolated mental health event, not related to terrorism.
“Officers worked immediately to detain the man and he has been taken into police custody,” Chief Superintendent Joseph McDonald said on Tuesday.
“There have been no reports of any shots fired, or any injuries to officers or members of the public.
“Officers remain at the scene and further inquiries are ongoing.”
Buckingham Palace declined to comment and said the incident was a matter for the Metropolitan Police.
Home Office minister Tom Tugendhat told Times Radio on Wednesday: "The police are, to put it mildly, all over it and our intelligence and other security forces are extremely aware of the challenges that we face and ready to deal with them – as the police did quite brilliantly yesterday."
A ring of steel is expected in the capital for King Charles’s coronation at Westminster Abbey on Saturday, as hundreds of thousands of people descend on the capital for the event.
Policing minister Chris Philp has described it as a “huge policing operation”, and heads of state and foreign royals from around the world are expected to travel to the UK.
Mr Tugendhat added: “What we’ve been planning for a number of months now is one of the most important security operations that the country has put into plan.
“The reason for that is this coronation is not just an opportunity to celebrate our new King, but also an opportunity to showcase the United Kingdom to the world.
“So we’re very conscious that there are going to be quite literally thousands, possibly hundreds of thousands of foreign tourists, there are going to be many film crews and journalists from around the world and of course, we’re going to have heads of state and government coming to celebrate with us on Saturday."
