With the UK's terror threat level at severe the cost of security for the first major royal wedding since 2011 is expected to reach up to £30million and the bill will be picked up by the taxpayer.
Thames Valley Police has asked well-wishers not to bring confetti to the procession amid fears the sight of someone throwing something towards the carriage could spark a security alert.
It is Thames Valley Police's biggest ever operation and they are relying heavily on Scotland Yard and MI5 for support.
It came as superfans camped on the streets overnight to secure their spots to see the procession through the Berkshire town tomorrow.
Armed police and specially trained sniffer dogs are patrolling the streets of the royal town, with squadrons of uniformed officers with machine guns toured the town in rotation.
Their colleagues are checking drains, bins and any other potential hiding places for bombs as the Berkshire town was turned into a fortress.
Thames Valley Police and the Metropolitan Police - who guard the Royals – used the dress rehearsal yesterday to assess any potential security threats or bottlenecks and crowd surges.
As many as 100,000 visitors are expected to flock to the Berkshire town this weekend - which has a population of 35,000 - to catch a glimpse of the newlyweds.
