A Hampshire police spokesman said: "The road is expected to remain closed for the rest of the day while collision investigators examine the scene and arrange for the vehicle to be recovered."
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The Conservatives have proposed a counter-extremism commission, while Labour would recruit more security and intelligence staff.
After a global IT crash caused chaos, BA says it aims to run a "near normal schedule" at Gatwick and the "majority of services" at Heathrow.
Georgina Callander's family said the government must "opens its eyes" in the wake of the attack.