Two nine-year-old boys have suffered serious head injuries after a tree fell on them while they were waiting for a turn to play cricket during windy conditions.
A third boy, also nine, had leg injuries after the tree fell at the Spencer Cricket Club in Fieldview, Earlsfield, south London.
A Metropolitan Police spokesman said: "We were alerted by the ambulance service at 16.04 that a tree had fallen on children at Spencer Cricket ground.
"The boys were waiting for a turn in the nets when the tree fell.
"Three boys were taken to St George's Hospital in Tooting. Two had head injuries and were in a serious condition. The third had leg injuries and was described as walking wounding.
"Wandsworth Council was been informed and attended."
A London Ambulance Service spokeswoman said emergency services were called at 3.45pm.
"We sent the London Air Ambulance, three ambulance crews, two single responders in cars and two duty officers.
"Our staff treated three patients, all reported to be nine-year-old boys."
Charlie Masson-Smith, from Wandsworth Council, said the wind was very strong today and could have knocked down a healthy tree.
"This was at a private cricket club but from what we have been told there were a bunch of kids queueing up to go in the nets. All of a sudden this tree came down on them.
"The council does not have any role to play, it is a private tree on private land but it has been pretty windy in town today and you can have a really healthy tree but if the wind catches in a particular way a healthy tree can be blown over.
"It is a terrible accident."
Spencer Cricket ground is home to the private Spencer Club, a sports club with more than 500 members offering cricket, tennis, squash, hockey and lacrosse.
According to its website, the Spencer Club was founded in 1872 when John Poyntz, Earl of Spencer and great grand uncle of Diana, Princess of Wales, was Lord of the Manor.
He permitted the founders of the club to drain part of Wandsworth Common and erect posts for cricket and the club was named in his honour.
It moved to its present location at Fieldview in 1903.