More than 40,000 Swansea City fans are at Wembley hoping to see the club promoted to the Premier League.
The Championship play-off final is one of the biggest games in the club's history and a win against Reading could net the Swans up to £90m.
The Swans have never played in the Premier League, and have not featured in England's top flight since 1983.
Most fans are travelling by road, with an estimated 200 coaches booked for the 1500 BST kick-off.
The match comes just nine years after the Swans almost went bust and eight years since they beat Hull City on the final day of the 2002/03 season to stay in the Football League.
"Emotions are changing a lot during the week, but looking back, the nerves are not as stressful as they were going back quite a while ago when we played Hull City," said Swans chairman Huw Jenkins.
"The build up to that game and the pressure involved and the fact that we were involved in the club at that time were far, far greater than they are today."
Supporters are travelling from all over the world to see the game including Canada, United States, Argentina, Trinidad, Russia, Germany, Holland, Thailand and New Zealand.
Garry George, is making a three-day trip from Australia.
"People obviously think I am a little bit mad, especially with the short turnaround and immediate return to work," he said.
The Swans received an initial allocation of 39,376 tickets for the final but were given extra after selling out in less than a week to take the total over 40,000.
Many fans are travelling up by road and should make it hassle-free as there are no planned works on the M4 on Monday.
British Transport Police's sector commander for Wales, Ch Insp Sandra England, said 1,500 fans were travelling on three football specials.
A further 1,000 fans had travelled up to London by rail on Saturday, she said.
"Everybody has been well-behaved and was looking forward to the match," she said.
However, those travelling by train and tube have been warned they risk missing the match if they are caught taking alcohol on board as they face being removed from services.
Messages of support
One fan who cannot make it though is Hollywood star Catherine Zeta Jones, who is originally from Swansea.
"Coming from a family of Swans fans from such a young age I wait with baited breath for the play-off final in Wembley," she said.
"I vividly remember the Swans when they were last playing top flight football in the early 1980s and loved every minute of it.
"My thoughts are with all the players and fans for this memorable day. Come on you Swans, let's do it again."
Swansea boxer Enzo Maccarinelli also sent a good luck message.
"The whole town is behind them," said the former WBO world cruiserweight champion.
"Everyone wrote them off at the beginning of the season so let's prove them all wrong and get them into the Premier League."
Rugby side the Ospreys have thrown their support behind their Liberty Stadium colleagues.
"They have earned their place in the final with some outstanding performances this season, and deserve their place at Wembley," said Ospreys managing director Roger Blyth.
"Swansea is a sports-mad city, and to have Premier League football and Wales' leading rugby region playing out of the Liberty Stadium will be something wonderful that all sports-mad people in the region will be able to gain great satisfaction from.
In Swansea, there are no planned events for match day, although supporters will be hoping for some kind of celebration should the Swans go up.
"The Swans have already done superbly well but promotion to the Premier League would be an enormous achievement," said Swansea council leader Chris Holley.
"It's a league that's watched by many millions of people throughout the world and means thousands of fans from across the UK and beyond would be coming to Swansea for the first time.
"It'd represent a wonderful marketing opportunity for Swansea Bay as a destination and would boost traders and accommodation providers across the area.
"Football is generating a magnificent feel-good factor across the city at the moment."