The collision took place in St John’s Street just after 3.30pm and resulted in a crashing through a wall of St John’s Car Park, say Northants Police.
Warwickshire and Northamptonshire Air Ambulance landed in Becket’s Park and was assisted by one of the Three Midlands Air Ambulances.
At 4.26pm Northants Police said: “Motorists are advised to avoid the area while emergency services respond to the incident.”
At 5.28pm an update from police read: “Motorists with cars parked in St Johns Car Park are asked to bear with emergency services and West Northamptonshire Council while work takes place to establish the structural safety of the building following this afternoon’s collision. Further updates will be posted once an assessment has taken place.”
At 5.48pm Northants Fire and Rescue Service said: “We have now left the scene of the incident at St John's car park in the hands of our colleagues at Northamptonshire Police.”
At 8.13pm Northamptonshire Police said: “Following the incident this afternoon, we have been informed that cars are now allowed to leave St John’s car park.
“The damaged entrance remains cordoned off so please use an alternative access point.
“Please be aware the car park is currently closed, and this may continue into tomorrow (Saturday). Please look at alternative parking if you are planning to visit the town centre.”

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The car smashed through St John's Car Park. Pic by Richard Theobalds Photo: Richard Theobalds

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The collision took place just after 3.30pm and resulted in a car colliding with St John’s Car Park. Photo: Abigail Lucy Zoe Silman. Photo: Abigail Lucy Zoe Silman

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One of the Midlands Air Ambulances landed in Becket's Park, assisting Warwickshire and Northants Air Ambulance. Pic by Richard Durham Photo: Richard Durham