When car dealership boss Iain Harris got the call from David Cameron’s security team that the Prime Minister was about to call in to buy a used blue Nissan Micra, he thought it was his mates winding him up. Harris, owner of Witney Used Car Centre, said he was asked if he would mind staying open for an extra half an hour on Friday night so the prime minister could look over the secondhand car, which cost £1,495.