In politics, there’s no such thing as a private conversation. Somebody really should have sent Jon Lansman the memo. The ‘Lansman Tapes,’ reported heavily in the press over the past two days, make explicit a direction of travel that has been obvious to any student or veteran of struggles with the hard left of British politics since long before they installed the most hapless of their number as leader of the Labour Party.

Behind Jeremy Corbyn’s increasingly threadbare ‘principled, honest politics’ routine, there was always a concealed cudgel. It’s a cudgel which is wielded by the same hard left cadres that made the Labour Party into kryptonite on the doorsteps of Britain in the 1980s and which did damage that took 18 years and four painful general Election defeats to undo. It’s a cudgel that the hard left – for all its professed love of ‘debate’ (and it does love to debate, endlessly, tediously, interminably amongst itself) – intends to use as a club against those sections of the party that refuse to endorse the half-baked pretensions and regurgitated dogma that they will insist upon calling ‘policies.’ And, thanks to Jon Lansman’s loose lips, it’s a cudgel that’s out in the open.

Nobody can be in any doubt after hearing the Lansman Tapes that Momentum – archly and accurately described by another writer for Labour Vision as nothing more than ‘Militant with lattes’ – has its sights set on total control of the Labour Party. It intends to take over regional party boards and amend the rules for the selection of MPs and councillors. It intends to force a change to the composition of the party’s NEC, to remove the balance between the various strands of the party’s coalition – trade unions, elected MPs and councillors, socialist societies and grassroots members – in favour of a structure that it can control. It intends to pass the so-called ‘McDonnell Amendment’ and finally repudiate Clause One socialism in favour of a beauty parade of hard left darlings that will view the essential work of changing society through Parliament as a distraction from the work of preparing a revolutionary vanguard – or ‘social movement,’ as they have now taken to calling it. And, proving that there is no crisis on the left that Len McCluskey cannot make worse, it intends to affiliate with Unite if he is returned as its General Secretary, obtaining organisational and financial clout beyond the dreams of any previous generation of hard left agitators.

Momentum intends, in other words, nothing less than the destruction of the Labour Party as we know it. The hard left has tried all this before, of course. In the 1970s and 1980s, the Militant Tendency – some of who’s leading lights are currently members of Momentum, it must be noted – tried to do exactly this. Never able to win on its own platform, the hard left from the Communist Party and Militant to the TUSC and Left Unity, has always tried to infiltrate Labour and seize control of it. To turn it away from the hard, messy, necessary work of winning support in the country and winning permission to change society, and turning it into an iron fist clutching a megaphone, agitating for a revolution that will never come and slapping itself on the back for the ferocity of its rhetoric even as its shouts fall on deaf ears.

There can, now, be no denying this. Jon Lansman’s unguarded statements, backed up by the testimony of Christine Shawcroft on Radio 4’s Today programme, make this clear – they have once and for all stripped away the cloak of ‘plausible deniability’ that the hard left operates under.

Momentum is merely a bridgehead for the kind of tactics that the Militant tendency and its descendants have been using for decades. With a bit of social media savvy, a well-run campaign and a latent desire for change among the party’s membership, it was able to convince enough of the party that it was a benign vehicle for ‘harnessing the enthusiasm’ of Jeremy Corbyn’s leadership campaign and creating a ‘kinder, gentler politics.’ Many – too many – were swept along in that initial wave of enthusiasm, genuinely believing that they were a part of something new and refreshing. It is them that the organised hard left has betrayed most of all.

The facade has been cracking for months. Elected MPs and councillors have been abused, sometimes in the most heinous terms, simply for expressing a different view. Social media has become a no-go area for too many activists – far too many of them young, or women, or LGBT – for fear of harassment and reprisal should they criticise the direction the party is taking. The poison of antisemitism, always lurking on the far left, has been allowed to seep into our ranks, with only lip-service paid to its eradication by the leadership. People with no connection to Labour’s historic values, the apologists and the revolutionaries and the sectarians, have used Momentum as a bridge into Labour politics – and the Lansman Tapes make clear that the organisation’s leadership has no intent of kicking them back out, whatever promises it publicly made to Corbyn.

Now, the facade is well and truly shattered. Momentum has played its hand. The role of the mainstream Labour Party and those who genuinely share our values – whether you call yourself a ‘moderate,’ ‘centre left,’ ‘soft left,’ ‘democratic socialist,’ ‘social democrat’ or any other label – is now clear. The hard left must be beaten, or the cost will be the Labour Party.

Most Momentum members and most Jeremy Corbyn supporters are reasonable people with a lot to offer Labour politics and the party’s best interests at heart. They have been led to believe that Momentum’s leaders do as well. They must be convinced that they have been lied to.

The McDonnell Amendment – named for a reason – must be defeated at conference in 188 days’ time. That innocuous-sounding rule change, and the other amendments to the party’s constitution pushed by the hard left, would break the Labour Party irrevocably as what it has been since 1900 – the only practical instrument that exists in this country for changing the majority of people’s lives for the better.

The rules surrounding leadership elections must also be clarified, to ensure that the ridiculous spectacle of a leader with no confidence among his colleagues gaining automatic entry to the ballot – a scenario never envisaged and one that the drafters of the rules did not intend to enable – cannot be repeated.

And, seeing as Momentum’s leadership makes it clear that it has no intention of rooting out the hard left in its own ranks, it cannot be allowed to join ours. Unite and Labour members must resist any attempt to formally affiliate to the organisation in its current state. The hard left has always been a parasitic force, and affiliation would be a charter for it to bleed dry everything that five generations of Labour men and women have built.

Many Labour members will, understandably, have felt angry and upset at hearing the Lansman Tapes and hearing the hard left’s plans for their party laid bare. Now, more than ever, we should remember the words of Joe Hill – Don’t get mad. Organise.