The strange case of Mark Field shows how the spectre of violence is destroying our political culture

What does the incident involving Mark Field and a protester at the Mansion House tell us about the state of our politics? I think it is a symptom of something disquieting, for there is a creeping, insidious tendency towards more intrusive, personal and, potentially, violent protests being undertaken in the name of causes that people feel are of such transcendent importance that they justify extreme measures – and, as has been discussed today in the response to those protests too.

These inflammatory political causes are, of course, Brexit (both for and against) and the climate change emergency. It feels, with both of these issues, as though we are edging towards a more violent culture. There is a difference between legitimate and illegitimate protest just as there is between legitimate and illegitimate methods of policing it, and we seem to be getting a bit confused about such distinctions.

As in the Mansion House, so far as can be seen, the protesters were purposely physically intrusive. Rather than waving placards outside the venue they wished personally to confront Philip Hammond and those attending the dinner and speech. Their reason? Because they held those attending responsible for crashing the economy a decade ago and crashing the climate now.

Right or wrong about that, the place to make such a protest is in public, where the right to protest is ancient, can be exercised peacefully with no restraint. The green movement can make its case at elections, on the airwaves and across traditional and social media. It can start new political movements. It can hold rallies. The opportunities to protest and campaign are not, in the UK, limited by some repressive regime and there is no need to invade places and disturb (deliberately or not) anyone’s peace.

Equally there is no excuse for improper "policing" of political uprising either – that it, taking things into one's own hands, as Mark Field was witnessed to do this week. Exercising protest in the normal way, using legitimate outlets, protects the rights and liberties of protestors. Sadly, this is more necessary than ever before. Though we are still protected by the rule of law, we are not short of thugs and bullies in the political sphere today. Personal safety has, sadly, become a key issue for everyone engaged in politics whether inside or outside of the Westminster "village".

It is no defence of Field to say so, but I do not believe any attempt to disrupt the proceedings of the Lord Mayor of London or the chancellor is fair game. If they are, then so is Caroline Lucas and Jeremy Corbyn.

MPs generally, and political activists to a lesser extent, have become the object and focus of hatred. For years there has been a rising trend of near-fatal attacks on MPs at their constituency surgeries. In recent months, hitherto obscure parliamentarians such as Anna Soubry who wanted to do no more than walk across Parliament Square to a BBC studio have been subjected to vile verbal abuse and threats. Death threats, Islamophobic, racist and antisemitic communications are received by MPs all the time – and I call these acts of violence too.

This rising tide of political aggression, a lack of tolerance on all sides, is why we should be careful – the media, protesters, and politicians – about the sort of language we use, even when faced with such momentous problems as Europe and climate change.

Political and industrial violence in the UK, and even mass civil unrest, is nothing new. Peterloo, Edwardian anarchists, Brick Lane and the Moselyites in the 1930s, the mass picketing in the 1970s, the riots in Grosvenor Square against Vietnam, running battles between fascists and anti-fascists since the 1950s, race riots, Grunwick, Orgreave, Wapping, Poll Tax riots, the terrorism of 7/7 and the long IRA campaigns, the Brighton bombing, assassinations and attempted assassinations, mass rioting in the 1980s and 2011, attacks on mosques, synagogues and temples…

What we are experiencing now is simply a recrudescence of the tendency for politics, in times of stress and controversy, to drift from debate to protest to direct action to verbal assaults to threats to more violence to terror. It is an eternal danger, and we are seeing it emerge again.