Captain described it as a "little incident"

“The British Airways flight to London was taxiing at OR Tambo International Airport when its right wing hit the building, injuring four people inside.

Images show the wing of the Boeing 747 wedged in the structure.

South Africa's Civil Aviation Authority said the aircraft had travelled down a taxi-way that was too narrow for it...
BBC News - British Airways wing clips S Africa OR Tambo airport building”