For many years, and to many people, Nigel Farage was UKIP. In the minds of a lot of voters I suspect he still is, despite it being over two years since his most recent stint as leader.

And for good reason. He played an essential role in giving UKIP its first breakthrough in the 1990s, in sustaining it through many difficult years, and then in its eventual period as a serious electoral insurgency. He became famous in the process, and developed into an instantly recognisable brand.

It must be said that he also worked hard and ruthlessly to ensure he retained his status as his party’s biggest fish, including in several bouts of vicious infighting. “Nigel always wins” was for 15 years or more a pretty good guiding rule of what would happen in any given internecine scrap.

But no longer. Twenty-five years after becoming a founding member of UKIP, the purple peril’s dominant figure has quit.

His given reasons are a grim reflection on the sorry and sickening state of the organisation he used to lead: it has become “unrecognisable”, “fixated” on the topic of Islam, and tainted by the presence of Stephen Yaxley-Lennon, AKA ‘Tommy Robinson’, the serially convicted founder of the English Defence League, and his attendant “entourage [which] includes violent criminals and ex-BNP members”.

It is to Farage’s credit that he has decided to leave in protest. While this site merrily tweaked his tail as ‘Sir’ Nigel Farage, and rightly argued that various of his views and decisions were wrong, it should be recognised that an under-reported feature of his work over the years was a sustained effort to fight off attempts by extremists to hijack his party. We often did not agree with Farage’s UKIP, and at times we actively disliked it, but it was a democratic political party which, eccentric and even counter-productive though it may have been, was not a fascist organisation like the National Front or BNP.

His strategic understanding that extremism would doom first UKIP and then Euroscepticism, and his general allergy to anyone of any views supplanting him in control of the party, combined to ensure that while various of his members said some pretty awful things over the years, he did at least act quite severely against far right entryists. The type of threat that he was up against, and his relative success in fighting it, can be seen in what has happened since he surrendered the leadership.

Farage is far from alone in resigning from UKIP due to the growing influence of Yaxley-Lennon and his allies. Well-known figures like Suzanne Evans and Patrick O’Flynn have quit in recent weeks, along with a sizeable number of rank and file members.

The problem is even worse than it first appears: the Tommyrot has not infected UKIP by sleight of hand, or due to unintentionally lax oversight of the party’s policies against entryism. Rather, Yaxley-Lennon has been invited in – warmly feted, even – by Gerard Batten, UKIP’s current leader, who has appointed ‘Robinson’ as an advisor and includes him in decision-making at the highest levels of his party.

Batten, a fellow founder of UKIP alongside Farage back in September 1993, was always somewhat ideologically at odds with his former leader. However, he managed to survive as an MEP since 2004, then steamed through the last two years of chaotic infighting before eventually taking over UKIP unopposed in April of this year.

That clear field is not proving healthy. Where Farage had to defend his leadership position from potential challengers by continually demonstrating electoral progress, Batten appears to feel free to indulge his long-standing hobby-horse of Islam, and has embraced a combination of Robinson’s street-mob politics and the YouTube activism associated with parts of the Trumpish alt-right.

While Farage famously helped Trump to celebrate his election victory in 2016, in more recent times he has exhibited some discomfort about the way in which the Donald’s former guru Steve Bannon has lauded people like the EDL founder.

This discomfort springs from the fact that Farage is not stupid. He may be wrong about various things, but his decades as a professional practitioner of small-party politics means he has a pretty good understanding of the instincts of UKIP’s target voters, and the binary choice between the route Batten is taking and mainstream electoral progress.

His resignation article laments the attendant fall in the bread and butter work of democratic politics – council by-election candidates, local organisers and campaigners on the ground – and touches on the reason it is particularly bad news right now:

‘These are the people organising the ‘Brexit’ march that is now advertised on the Ukip website. My heart sinks as I reflect on the idea that they may be seen by some as representative of the cause for which I have campaigned for so much of my adult life…There was one last opportunity to stop Ukip being part of this probable travesty, which may well inspire violence and thuggish behaviour and, with it, give the opponents of Brexit a chance to lambast Brexiteers everywhere…We are now just a few days away from the most ill-judged political event I have ever been aware of in British politics. The very idea of Tommy Robinson being at the centre of the Brexit debate is too awful to contemplate.’

In other words, Farage fears – rightly – that ‘Robinson’, having hijacked UKIP as a vehicle for his personal jihad, will try to hijack Brexit, and in so doing smear and discredit it with all the vile associations which so many Eurosceptics fought for so long to keep it separate from. Batten has invited the worst possible people in, at the worst possible time for the cause Farage cares about most.

The “one last opportunity” referred to in the above quote was an attempt to get UKIP’s NEC and its MEPs to obstruct Yaxley-Lennon’s appointment, and potentially even unseat Batten in the process. But, breaking that once iron law, Nigel did not win. He lost. And therefore he is off.

This has real world implications, too. The incompetence of Farage’s various successors, and now the bad judgement and poisonous friendships of UKIP’s latest leader, have all-but demolished the party as an electoral threat to the pro-Brexit right of the Conservatives. Batten’s UKIP polls at around four per cent, and I suspect a good chunk of that is people who believe they are voting for Farage.

That weakness bolsters the confidence of Downing Street in trying to ignore the concerns Tory MPs, members and voters have about the Prime Minister’s EU deal. Where Cameron once assumed his critics on the right had nowhere to go, only for UKIP to prove him wrong, May now has reason to think that if UKIP is too unpalatable even for Farage then she really can afford to disdain the Brexiteers.

It’s not impossible, of course, that this might not be his last throw of the dice. Might we see the old warrior return to the field in a new guise, in the hope of establishing a new threat on the right before it is too late? It would be hard, perhaps even impossible, but we can’t entirely rule it out.