LONDON, March 29 (Xinhua) -- A 30-million-pound "ring of steel" will surround the wedding of British Prince Harry and Meghan Markle, including barriers, vehicle checks, snipers and airport-style scanners, at Windsor Castle in May, it was revealed here Thursday.

More than 100,000 people are expected to visit Windsor, Berkshire, for the big day on May 19, and they should expect to be stopped and searched by police.

The "ring of steel," which costs about 42.18 million U.S. dollars, will be erected to deter terrorist vehicle attacks, said Thames Valley Police, responsible for policing the event, adding that the operation is likely to be the biggest in its history as they gradually build up the security in the city over the next seven weeks.

It takes about 44 minutes to travel from London to Windsor Castle. Approximate driving distance between London and Windsor Castle is 37 kilometers.

"STOP AND CHECK"

Announcing the first details of the security operation, British police said that motorists driving into Windsor face being stopped and checked. All those arriving in the town will go through a "a screen and search regime."

A huge security boundary will be mounted around the castle and St George's Chapel, where the wedding ceremony will be taking place in front of 600 guests.

The mounted section, roads policing unit and the National Police Air Service will also be joining in the security operation over the coming weeks.

Police will also use a network of automatic number plate recognition (ANPR) cameras to check for stolen or suspect vehicles on criminal databases.

All those entering the inner area to see the royal procession will be subject to airport-style screening with routine bag searches while checks will also be mounted on commercial vans and lorries.

The measures are intended to guard against the threat of terror attacks using vehicles and other weapons on dense crowds of spectators, as well as protecting the royal family themselves.

MORE POLICE PRESENCE

The police presence in Windsor has already started to increase, with the arrival of unarmed and armed officers, search dogs, mounted police, the roads policing unit and helicopters.

A police spokesman said, "Residents, local businesses and visitors to the town can expect to see an increased police presence, police officers, both armed and unarmed, search dogs, the mounted section, the roads policing unit and the National Police Air Force."

On the day, armed officers will mingle with the crowds while snipers will be deployed on rooftops.

All leave for the 4,200-strong police force has been cancelled as they work with Scotland Yard, which will provide security for the royals inside the castle.

Dogs and mounted patrols will be on patrol, specialist firearms units are being brought in and marine officers will carry out searches along the River Thames.

Police and security chiefs have been studying lessons learned from the five terror attacks in London and Manchester last year, in particular the atrocities on London and Westminster bridges where vehicles mowed down crowds.

Police said that they are trying to balance robust security measures with a desire to allow the thousands of onlookers to enjoy the atmosphere of the wedding.

Specialist units, such as firearms officers, are to be brought in as re-inforcements from neighboring forces.

Other forces including the Metropolitan Police and Surrey Police are supporting the operation and specialist units are moving in from across the country.

Assistant Chief Constable David Hardcastle, leading the security operation for the wedding, said that his force has a long history of policing royal events including the annual Windsor Garter Ceremony, state visits and the Aueen's birthday.

"The wedding of Prince Harry and Ms Markle is no exception," he said.

So far, there is no intelligence of any specific security threat to the event, news reports said Thursday.

However, police and security officers are acutely aware the event will be a major target at a time when the terrorist at a time when the terrorist threat level remains at "severe" in the UK, meaning an attack is "highly likely."

"We are working with our partners, local businesses and the community to deliver a safe, secure and happy event for everyone," he said.