No one's borders were open in 1974 but Lord Lucan was able to kill his children's nanny and get clean away. It helps to be posh, it's true, but still he was never found in the United Kingdom and in 1974 there was no channel tunnel.
In 2016, Europe's (but not the UK's) borders are open and Anis Amri got from Berlin to Milan before he was stopped and shot. Would it have been better if the borders were closed?
I don't think so. Consider that the UK does not have a single police force, just lots of local constabularies - some of them incompetent and, as official reports frequently also tell us, corrupt. Commit a crime in Cumbria and flee to Cornwall and you are moving from the territory of one police force to the territory of another. So should the borders be sealed as you move from one constabulary area to another?
In July 2005, Mohammad Sidique Khan was able to travel by train from Leeds to London and blow himself up on the London Underground. He and his friends killed 52 people in their attack. Does that mean you shouldn't be able to travel by train from Leeds to London without being stopped at whatever is declared the border between North and South?
Europe's open borders are a huge political achievement. They enormously improve business productivity - lorries travel faster - and they make holidaymaking and even simple day trips more pleasant. Just compare driving from France to Germany with driving from England to France (and back).
Those who want to close the borders don't tell you one important thing: they assume that they themselves will use the VIP channel, likely in coming years to become a lucrative business. Buy shares now and profit from discrimination against the ordinary traveller who of course is now likely to vote for more sheep pens like they have already at Calais. British holidaymakers assume that it is only natural to wait and wait before they are allowed back into their own country.