Thousands of excited football fans have arrived at Wembley Stadium for the Champions League final.
The Manchester United v Barcelona game is due to kick off at 1945 BST.
Supporters of both teams have been congregating outside the ground, where a huge police operation is under way to ensure the game passes peacefully.
The game is set to be the most-watched fixture between two club sides ever, with up to 300m people expected to view it worldwide.
The bumper viewer figures are expected partly because the final is to be held on a Saturday for only the second time, and also because both clubs have such a huge following.
It is being billed as the biggest sporting event in the UK until the London 2012 Olympics.
Fifa president Sepp Blatter has said he will not attend the game because he is preparing for an ethics committee hearing following bribery allegations.
Blatter has not commented on the proceedings but said: “The facts will speak for themselves.”
Some 1,000 police officers are involved in the operation across London. So far there has been no trouble, according to a Metropolitan Police spokesman.
The Met has revealed that officers from the Spanish force will be on duty in London during the game.
“A Catalan speaking officer from the Met will be liaising with the Spanish police during the event and will be on hand to assist with fans if required,” a spokesman said.
“Police spotters from Greater Manchester Police and Spanish police will be working alongside uniformed Met spotters.
“If you are subject to a banning order and you attempt to get into the ground you will be arrested.”
Each club has 25,000 supporters with match tickets, although an estimated 110,000 fans were expected to travel to London for the final.
Pubs in the area closed an hour before kick-off and no alcohol is being permitted inside the stadium.
Neither team is missing any star players.
Sir Alex Ferguson has decided to start with Javier Hernandez up front, alongside Wayne Rooney.
Sir Alex must also decide whether to man-mark Barcelona’s most feared player, Lionel Messi – often considered the best footballer in the world.
Many fans are trying to acquire last minute tickets outside the stadium.
Dave, a Manchester United supporter, said: “All the Spanish fans have been great and having a really great time – they are really friendly.
“I would have travelled to the other side of the world just to savour the atmosphere.”
Barcelona supporter Mark said: “It is fantastic to be here. It is a great opportunity for all the people of Barcelona and Manchester.
“I hope it will be a good match.
“We have fantastic players but Manchester United are a very good team – it will be an equal match.”
Earlier in the day Barcelona fans gathered in London’s Trafalgar Square where Nelson’s Column was festooned with flags.
A major policing operation is also taking place in Manchester.
Extra patrols are being carried out in the city centre as supporters fill pubs and bars to watch the match.
Supt Chris Sykes, from Greater Manchester Police, said: “Our main aim is to ensure the weekend and bank holiday is a safe and enjoyable experience for everyone.
“There will be a lot of Manchester United fans, and football fans in general, hoping United will be able to overcome Barcelona.
“Obviously emotions can run high, but what I’d say is make sure you take care of yourself when out and about.”