Police have tightened and revised security at Wimbledon because the Centre Court could be more open to attack now that its upper levels have been removed for renovations.

"Surrounding areas are now under closer scrutiny," said Superintendent Peter Dobson, who added that no specific threat has been issued to players or spectators.

But, with the roof off the world's most famous tennis court in preparation for construction of a retractable cover, the royal box and its VIP guests are now much more exposed.

• Images from day one

"It could provide greater vulnerability," Dobson said of the court that was fully open to the elements on a chill, windy and rain-interrupted opening day on Monday.

In fine-tuning security for Wimbledon 2007, police played out one possible scenario that they needed to counter -- an aerial attack.

The Civil Aviation Authority would immediately alert Wimbledon if there are any unusual air movements in the area and police could call on spotter planes and helicopters to monitor the situation, Dobson said.

"Every year we do change our tactics slightly. We renew them and we refresh them. But mainly we change our tactics so if someone was trying to attack the venue they have something new to defeat every year," Dobson told reporters.

On a lighter note, police promise to deal sternly with any streakers who might be tempted to leap on to Centre Court as one did last year in a quarter-final match between Russia's [Images] Maria Sharapova [Images] and Elena Dementieva.

"We have a robust plan for dealing with them. Stewards have been trained specifically to deal with streakers," Dobson said.

• Wimbledon Championships 2007
• Complete tennis coverage
• All you want to know about Sania Mirza