Roads in front of Buckingham Palace will be shut during the daily Changing of the Guard ceremony starting on Wednesday following the truck attack that killed 12 people in Berlin, British police said.
The military ceremony regularly brings crowds of tourists outside the gates of Queen Elizabeth II's residence in central London and previously there have only been some traffic restrictions while it takes place.
London's Metropolitan Police said the closures were a "necessary precaution" because of "the event's high profile in an iconic location with a substantial military presence and attracting large crowds".
The closures had already been planned for a three-month trial period but police said this was being brought forward after a truck ploughed into a crowded market in the centre of the German capital on Monday.
"The planned implementation has been brought forward following the events" in Germany, the police said in a statement.
"Alongside the road closures, additional barriers will be in place to maintain security for the guard movements."
The police stressed the security plan was being implemented as "a precautionary measure and not in relation to any specific intelligence".
Some police forces in Britain have said they would step up checks following the Berlin attack and the Metropolitan Police have said they are keeping their security planning "under review".
The current threat level set by Britain's security services has been at "severe", meaning an attack is "highly likely", since 2014.