That's certainly a good question one day after the Rolls Royce that Prince Charles and his wife were riding in was attacked by those protesting a stiff increase in tuition fees at U.K. universities.
One thing that could have been done, one security expert tells the BBC, is to have used a different car:
"Former royal protection officer Ken Wharfe told the BBC the royals' 'shiny brown limousine' was 'a challenge' the crowd couldn't resist — and once it became a target, escape was very difficult. ... 'I do think this was the classic example where the Prince of Wales should have been using his armored Bentley — it's far less conspicuous.' "
Perhaps the royals could have been taken to their destination via a different route, of course.
The Guardian writes that Prime Minister David Cameron on Thursday "admitted concerns over royal security must be addressed, but said the responsibility for violence lay with the protesters. 'We want to learn the lessons from that but, above all, we want to make sure that the people who behaved in these appalling ways feel the full force of the law of the land.' "