Anthony Joshua and Wladimir Klitschko's heavyweight world title showdown will be watched by a record-breaking 90,000 fans in attendance at Wembley Stadium.
Undefeated Joshua will put his IBF title on the line against the division's former ruler Klitschko on April 29, with the WBA and IBO heavyweight belts also up for grabs.
Each batch of the initial 80,000 tickets sold out in under an hour.
But the postponement of engineering works on London's rail network and additional services - after intervention from Mayor Sadiq Khan - has secured an extra 10,000 seats and a post-war British record crowd.
Promoter Eddie Hearn said: "I'm delighted that the capacity for Joshua vs Klitschko has been increased to 90,000 making it the biggest live gate of all time at the new Wembley stadium.
"I want to thank Wembley, [Transport for London] and Brent Council and particularly the Mayor of London, Sadiq Khan, who has fought our corner to ensure a capacity crowd will get the opportunity to watch this event live in the capital.
"At the boxing writers' dinner last year, Sadiq urged me to bring the biggest fights possible to the city and I'm delighted to have the biggest fight in British boxing history at Wembley Stadium on April 29."