The proximity of the 800th anniversary of Magna Carta next year makes Boris Johnson's Telegraph column from Sunday even more shocking. His plan to arrest anyone who travels to Syria or Iraq without 'good reason' utterly abandons the presumption of innocence. Instead, all travelers would be presumed guilty – and guilty of the extremely serious charge of terrorism – unless they could somehow convince 'the authorities' otherwise:

We also need to be far more effective in preventing British and other foreigners from getting out there…We need to make it crystal clear that you will be arrested if you go out to Syria or Iraq without a good reason. At present the police are finding it very difficult to stop people from simply flying out via Germany, crossing the border, doing their ghastly jihadi tourism, and coming back. The police can and do interview the returnees, but it is hard to press charges without evidence. The law needs a swift and minor change so that there is a “rebuttable presumption” that all those visiting war areas without notifying the authorities have done so for a terrorist purpose.

Boris of course has the laudable aim of curbing the jihadists. But that is just the sort of ambition that has excused too many careless erosions of our ancient freedoms. Already he calls for the return of control orders and laments how hard it is to press charges against British citizens without evidence; as if the assumption of innocence until proven otherwise has not acted as the ultimate safe-guard of citizens against radicals throughout modern history.

According to the Mayor, such controls and assumptions need merely a 'swift and minor' change in the law. Are our Magna Carta liberties to be so swiftly and so triflingly abandoned?