Speaking after this afternoon's crash, Nottinghamshire Police issued this statement.
"A police vehicle responding to an emergency call has been in a collision with another vehicle in Nottingham this afternoon.
"A man and a boy have been taken to hospital. The male police officer was uninjured.
"An investigation has begun and is on-going."
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Dry overnight, rain by tomorrow afternoon.
Dry with clear spells overnight, cool in rural areas.
"She tried to take hold of the knife to stop him. He told her not to shout out and scream and get on her knees and beg."