Security at Wimbledon is being stepped up after the recent UK terror attacks involving vehicles hitting pedestrians.
The measures include the installation of concrete roadside barriers to protect tennis fans outside the venue.
The Met Police says the plans will also see firearms officers in and around the grounds and a mobile unit which can “respond to emerging incidents”.
Tournament organisers say there has been a “proportional uplift” in measures introduced in past years.
About 7,000 people were queuing outside the All England Club on the first day of the championships.
Wimbledon said the use of the barriers was part of “enhanced measures” this year and would provide “visible physical security”.
They have been placed along the route people take as they make their way to and from the tournament as well as in the public queuing zone.
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Vehicles were driven at pedestrians on Westminster Bridge in March, on London Bridge in June and near a Finsbury Park mosque later the same month.
The Met Police said it “continually develops and refines plans for this type of event and planning has been under way throughout the year”.
“We have put together a proportionate policing plan with a significant number of resources to support the club to deliver a really safe, secure competition,” said Supt Jo Edwards.
“Our plans are based on a number of factors, including the threat level and recent events in London and the UK.”
She said officers will be working in uniform and plain clothes during the two-week event.
Police also warned the public against pick-pockets and touts selling unauthorised tickets.
Wimbledon has published security advice on its website, saying there would be extensive searches of people, bags and vehicles and urging spectators to allow plenty of time for entry.
The tennis club has continued its ban on spectators bringing in selfie sticks or any “objects or clothing bearing political statements”.
The Championship 2017: Banned items
- Any bag exceeding 40cm x 30cm x 30cm (16in x 12in x 12in)
- Hard-sided items of any size
- Any item which may be interpreted as a potential weapon including sharp or pointed objects – such as knives or large corkscrews – and “personal protection” sprays
- Large flags (over 60cm X 60cm, 2ft x 2ft), banners, rattles, klaxons or oversized hats
- Any objects or clothing bearing political statements or commercial identification intended for “ambush marketing”
- Selfie sticks