Commuters, including a cancer patient who needed medical attention, were left stranded for three hours after a train hit a tree that had fallen on the line in south London.The incident happened at West Wickham at around 5.30pm on Wednesday with engineers and the London Fire Brigade both sent to the scene.Footage shows two trains were brought to a standstill after part of the tree became wedged in a wheel, while other trains were cancelled, delayed or revised.