Mega security plans for Prince Harry, Markle wedding in UK

UK Police are urging the public not to be "alarmed" by the massive scale of security arrangements ahead of the wedding of Prince Harry and Meghan Markle, described as one of the largest security operations in British history.

Prince Harry and Markle would wed at St George's Chapel, Windsor Castle on May 19, followed by a carriage procession through Windsor town and a reception in St George's Hall, it was announced last year.

Thames Valley Police called on the public not to be "alarmed" by the massive scale of the security arrangements in the lead up to the big day on May 19 in Windsor Castle.

"The wedding is expected to attract thousands of people from around the world to Windsor and planning is well under way. Visitors to the town can expect to see our officers, both armed and unarmed, our search dogs and our mounted section out and about in the coming weeks and months," Thames Valley Police said in a statement.

"A broad range of visible security measures are already in place, such as the extensive network of Automatic Number Plate Recognition (ANPR) technology, Close Circuit Television (CCTV) and Hostile Vehicle Mitigation (HVM) barriers. There are also many security measures that you can't see," it said.

The force also encouraged local businesses, communities and visitors to continue to be its "extra eyes and ears".

British Transport Police will be patrolling railway stations and carriages linking other regions with the town of Windsor.

Visitors for the wedding will have to pass through airport-style security scanners, and steel barriers will be erected to deter terrorist vehicle attacks, something police termed as a "screening and search regime".

Dogs and mounted officers will also be on patrol and marine officers will be conducting searches along the nearby Thames river.

All leaves for Thames Valley Police's 4,200-strong force has been cancelled, though police are refusing to say exactly how many officers will be deployed in the security operation.

The force is working closely with Scotland Yard, responsible for the security of the royal family inside Windsor Castle.

The wedding day will feature regiments and units that have a special relationship with Prince Harry, who served in the military for a decade and was deployed on frontline duties twice in Afghanistan.

According to some estimates, the security operation for the royal wedding could amount to 30 million pounds.