A child was found wandering on the train tracks after her great-grandmother was hit by a train on Wednesday, July 1.
British Transport Police (BTP), London Fire Brigade and Kingston police were called to Hampton Wick station at about 11.50pm, after reports a woman was struck by a train.
The 72-year-old woman was transported to St George's Hospital with mulitple injuries, where she remains.
The railway line was closed until about 1.25am on Thursday when it was handed back to Network Rail.
A BTP spokesman said: "It appears that the woman, who is from Shepperton, Surrey, was struck after attempting to cross from one platform to another.
"The woman was crossing the tracks with a seven-year-old relative, who was uninjured. The family has been informed."
The incident, which involved the 11.41pm empty stock service from Shepperton to Wimbledon, is not being treated as suspicious.
Witnesses are asked to call BTP on 0800 405040 quoting incident one of 2/7/09.
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