The driver, a 42-year-old female ambulance technician, and the patient, an 88-year-old man, were pronounced dead at the scene.
A male crew member and a male relative of the patient remain in hospital both in a serious condition.
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The two new owners of the South West Trains franchise have promised extra seats, new trains and faster journeys for passengers from August.
Monday afternoon's forecast for the east of the region
Monday afternoon's forecast for the west of the region