Wimbledon officials have beefed up security after a little-known protest group tried to stage a demonstration within the ground.
Democracy campaigners 15M London - which has a movement in Spain, where it originated - attempted to smuggle banners and tins of paint inside SW19, where it was feared they would target a high-profile match.
The 14 protesters, all Spanish and wearing yellow T-shirts, sent the grounds into lockdown with a Metropolitan Police helicopter monitoring the massive queue. It was feared the group would target world number one Rafael Nadal who was playing on Court One.
Thousands of fans - who had already queued throughout the night in the hope of seeing some of the top stars play - were delayed as bosses closed the gates for an extra 45 minutes.
Ian Ritchie, chief executive of the All England Lawn and Tennis Club, said it was not known if the 125th championships would be targeted again but security had been increased.
He said: "We put a particular message out looking at strengthening the presence on the court. We have service stewards from the armed forces - we have 650 of them.
"They are hugely equipped to deal with the situation as well as the G4S security. For all we know, we have to be prepared for people coming back in on Monday."
A police spokesman said: "At approximately 10.30am today a number of people were stopped in the queue at the tennis for Wimbledon and items were also found near to this group, believed to be for use in a demonstration or publicity stunt.
"The police informed the All England Lawn Tennis Club which delayed the opening of the gates where additional searches took place. A number of individuals are not being allowed access to the tennis following the searches. No arrests were made."
15M London put a message on its website saying: "Important: don't go to Wimbledon - mission aborted." The activists describe themselves as "a movement of outraged citizens" fighting for people rather than economic powers.
Photo by MDales, Press Association