The theatre's annual report for 2008/09 reveals that its production of War Horse took £2.7 million at the box office and filled 99 per cent of available seats.
Scenes from War Horse.
Leading the charge was War Horse, an adaptation of Michael Morpurgo's novel that tells of the bond between a young recruit, Albert, and his horse, Joey, during World War 1.
The smash hit, playing at the West End's New London Theatre, in Drury Lane, includes life-sized puppets of horses built by a South African company, the Handspring Puppet Company. The puppets are operated by the actors.
Morpurgo, writing about War Horse on the website promoting the production, said the novel arose from a chance conversation in his local pub nearly 30 years ago with an old soldier who had been to the World War 1 as a 17-year-old "with 'orses".
"Then there was the discovery that over a million horses died in that dreadful war - and that was just on the British side - and that most of them that survived were sold off after the war was over, to butchers in France.
"The book nearly won the Whitbread Prize but didn't, and then languished, rarely read thereafter for 25 years but kept in print by kind publishers all this time.
"In 2005, unbeknown to me, Tom Morris at The National Theatre was looking for a way to bring Handspring Puppets to the theatre.
"These unique puppeteers from South Africa made life-size puppets who take centre stage in their shows.
The play is based on the book War Horse, by Michael Morpurgo.
Morpugo said he witnessed some of the difficulties in getting the production to stage, but everyone saw the potential to create a unique theatrical experience.
"It was a hard road, but everyone seemed utterly determined to make it work. And did they make it work?"
Two sold-out seasons speak for themselves.
There are plans to take War Horse on tour in Britain and internationally, ending on New York's Broadway.
The horse puppets are made of cane, bent on to plywood shapes, and bound together with twine and covered in translucent fabric.
Some of the horses are fully articulated, with two interior and one exterior manipulator. Because they have aluminium spinal structures, they can carry human riders.
Some of the horses in the production are more abstract, with no legs and only one manipulator.