It is easy to suppose that the frightening bear pit of American politics is a long way distant from our own, more civilised democracy – particularly when there has been an upsurge of partisan violence across the Atlantic.

Thank goodness the pipe bombs posted to Barack Obama, Hillary Clinton, Joe Biden and others on the liberal wing of US politics were intercepted by the FBI and the intended victims survived unscathed.

But this outrageous assault on life and decency should serve as a warning not just to Americans about the deadly potential of political aggression, but to us, too.

None of the 14 crude bombs sent to prominent Democrats and public figures detonated, possibly because they were poorly designed

The 56-year-old suspect behind the packages, Cesar Altier Sayoc (left and right) is said to be obsessed with looking young and asked a lawyer about changing his legal age in court documents. He is a former bodybuilder and has worked in strip clubs

Sayoc posted many pictures of himself in strip clubs, and may have worked in one. He is seen with an unidentified woman

After all, it is here in Britain that, as last week’s Mail on Sunday revealed, one Brexit rebel warned Theresa May she should ‘bring her own noose’ to a meeting with Conservative back-benchers.

Another anonymous briefer told The Sunday Times that ‘the moment is coming when the knife gets heated, stuck in her front and twisted. She’ll be dead soon.’

This sort of language is not just disgusting, it is corrupting and infectious. Today’s Mail on Sunday reveals how Labour MP Caroline Flint – who, like me, campaigned for Remain but accepts the referendum result – has now been threatened in similar terms on Twitter, being told: ‘Next year you’ll be hanging from a rope.’

It is profoundly troubling.

People have rightly been repelled, and I suspect politicians will now be more careful, for a while at least. The Labour MP Jess Phillips has already apologised for saying she wanted to stab Jeremy Corbyn in the front.

This sort of language is not just disgusting, it is corrupting and infectious, writes Damian Green. Britain's Prime Minister Theresa May leaves after a news conference at the European Union leaders summit in Brussels

Yet the atmosphere in Parliament remains so poisonous that several MPs have told me they are even avoiding the Tea Room – which normally serves as a relaxing canteen – because they can’t stand the thought of having to sit next to certain colleagues.

The dangerous aggression now demeaning British politics is by no means confined within the Palace of Westminster, however.

Some members of the public are losing all sense of decency and self-control, and this wider aggression is particularly destructive.

The very first email I opened on Friday, for example, demanded that the Government’s Brexit negotiator Olly Robbins should be ‘strung up’.

There was a time when most MPs would have expected a threat or a serious insult from members of the public perhaps once or twice a year. Now, thanks partly to the internet, we receive them every day. ‘Go f*** yourself’ is wearyingly common.

Yes, there are more serious problems than rudeness, particularly towards politicians. But it is time to recognise that the violence of public rhetoric has reached a new and dangerous level.

Remember, there are some people who treat this talk of knives and nooses as a call to action.

For several years I was bombarded with racist emails, using the N-word and complaining about ‘politician traitors’, from a constituent who gave his name. He didn’t directly threaten me, so I just ignored them.

Then I discovered that a police investigation into other matters had revealed he kept an unlicensed gun at his home.

I am more careful these days.

'Thanks partly to the internet, we receive [abuse comments] every day. ‘Go f*** yourself’ is wearyingly common', writes Damian Green. He says there are some people who treat this talk of knives and nooses as a call to action

It is little more than two years since Jo Cox MP was murdered in her own constituency by an extreme Right-wing killer, and that was not an isolated incident.

In 2010, Stephen Timms MP was holding a surgery in a local community centre when he was stabbed in the stomach by a 21-year-old woman student who was taking revenge, she said, for the Iraq War. Thankfully, Stephen survived and was able to resume his full parliamentary duties.

Before that, an aide to the former MP Nigel Jones called Andy Pennington had been stabbed to death at a constituency surgery in Cheltenham.

I now take security precautions at my office and at home, which were simply not necessary when I first became an MP.

The mood at Westminster is one of gathering gloom across the parties. Sensible people on all sides say that we must clean up our own act and turn down the volume, but persuading millions of others to do the same is not so easy.

There are those who say that we can happily ignore the lies and menaces spread on social media, that what appears on screen really doesn’t matter, that anything goes on the web, and so on. But such people have their heads in the sand. However shallow the anonymous rantings of social media might seem, they affect the real world, too.

And this brings us back once again to events in America, a place where politics now involves bombs and weapons.

President Trump, the master of divisive rhetoric, has played an inglorious role. He plumbed new depths of personal attack when he whipped up crowds against Hillary Clinton, calling her ‘Crooked Hillary’ and encouraging chants of ‘Lock her up’.

His response in the aftermath has been to blame the media for fomenting discord, a stance which takes a degree of nerve on his part.

As last week’s Mail on Sunday revealed, one Brexit rebel warned Theresa May she should ‘bring her own noose’ to a meeting with Conservative back-benchers

But Trump is not the only guilty party. Neither Left nor Right has a monopoly of virtue when it comes to smearing opponents. In the run-up to the 2014 Scottish referendum, the so-called ‘Cybernats’ filled the internet with hatred of their Unionist opponents.

The Brexit referendum and its aftermath have followed the same course. If you only took your news from social media (as too many people now do), you would assume that all Brexiteers were racists who hated the modern world, or that all Remainers were out-of-touch intellectuals who loathed Britain.

This is no way to bring the country together.

These are dark times and we must all play our part in trying to alleviate the climate of aggression. However much we may disagree, others have a right to their point of view.

For unless we establish a more civilised political conversation, and urgently, we will find ourselves condemned to a debased and potentially lethal form of politics – as Americans know all too well and, as I fear, we will soon discover for ourselves.