Over 18,000 people this morning tried to buy tickets for the Miss Saigon anniversary gala on 22 September, causing the ticketing website to go down.
The special performance, which saw tickets being sold at the 1989 prices ranging from £13.50 to £22.50, sold out in minutes, leaving many fans venting their frustration on Twitter.
Fans queued outside the Prince Edward Theatre, which holds a total of 1,700 people, this morning as the Delfont Mackintosh website crashed due to high demand.
The gala performance will bring back some of the original cast members for a special finale.
For eager fans who missed out on tickets, there will be a limited number of day seats available on the morning of the performance, as well as being recorded for BBC Radio 2 - playing on 28 September 2014.
Boublil and Schonberg's musical transplants the Madam Butterfly story to war-torn Vietnam. Cultures and aspirations clash when a local prostitute meets her GI Joe during the fall of Saigon in 1975.