A “substantial” policing operation will be in place during Trooping the Colour, with an anti-monarchy group banned from using amplified sound.
The Princess of Wales has announced she is joining her family in marking the King’s official birthday during the event at Horse Guards Parade near Buckingham Palace in central London on Saturday.
Kate has been receiving treatment for an undisclosed form of cancer since late February and the major national event will mark a return to the public spotlight.
Hundreds of Metropolitan Police officers will be deployed along the ceremonial route to ensure the safety and security of attendees amid a planned demonstration by pressure group Republic.
Scotland Yard has imposed a condition under Section 14 of the Public Order Act 1986 prohibiting protesters from using systems to amplify sound “within the footprint” of Trooping the Colour between 8am and 3pm.
Chief Superintendent Colin Wingrove said: “Trooping the Colour holds national significance and as you would expect with this ceremonial event there is a substantial security operation to ensure everyone who attends and participates can do so in a safe and secure way.
“Alongside colleagues at the Ministry of Defence and the Royal Parks, our policing plan has focused on achieving this aim.”
He added: “It’s imperative this event is safe, which is why along with our partners we have considered factors, such as how amplified noise could disrupt and impact mounted regiments taking part.
“We have also taken into account the views of Republic. Our concern, along with partners, is that amplified noise could cause a public safety issue and serious disruption to the event and crowds attending.
“That is why the Met has taken a considered decision to impose a condition prohibiting amplified sound.”
Republic, which campaigns for the abolition of the monarchy and its replacement with a directly elected head of state, said the protest will go ahead without amplified sound.
Chief executive Graham Smith told the PA news agency: “We don’t agree with their reasons but we have to go along with it because otherwise we’ll be arrested.
“It isn’t a big problem, we’ve got quite loud voices.”