I’M old enough to remember seeing the BBC’s Wednesday Play of November 16, 1966. It was entitled Cathy Come Home and was by a writer called Jeremy Sandford and directed by an amazing talent by the name of Ken Loach.

The performance was a searing indictment of Britain’s then chronic, bone-crushing housing shortage. The plot (played out in grainy black and white) follows the eponymous Cathy as she spirals downward from being a young, married mother living in a new flat “with parquet flooring and tin openers fixed to the walls” to being homeless and alone. In a final scene I still remember, her children are forcibly taken from Cathy by social services.

Such a brief description fails to convey the power of Cathy Come Home. It was path-making TV – gripping, never patronising, and with an insider’s understanding of working-class life. Filmed on location with handheld cameras, it created a naturalistic style that would become Ken Loach’s trademark for the next five decades.

It was no surprise that the play caused a political storm and at the same time made Loach’s reputation as a film-maker. In 2000, the British Film Institute voted Cathy Come Home the best-ever TV drama.

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At the weekend, the Labour Party expelled Ken Loach from its membership. His political sin appears to have been an unwillingness to disown other left-wing Labour members expelled by the party in recent weeks – a move 85-year-old Loach has described as a “witch hunt”.

Thus Britain’s (and Europe’s) most distinguished political filmmaker has been booted out of the Labour Party by Sir Keir Starmer – not for organising a faction, but merely for suggesting that being a socialist is not sufficient grounds for having one’s party card withdrawn.

Former Labour shadow chancellor John McDonnell tweeted: “To expel such a fine socialist who has done so much to further the cause of socialism is a disgrace. Ken’s films have exposed the inequalities in our society, have given us hope for change & inspired us to fight back.

I send my solidarity to my friend and comrade.”

Keir Starmer was only four years old when Cathy Come Home was first shown. Loach went on to direct a stream of innovative political and social dramas including Up the Junction (about the lives of young working-class women), The Big Flame (about Liverpool dockers), Days of Hope (about the General Strike), and The Price of Coal (about a colliery disaster).

As mainstream television became more unwilling to present dramas with a working-class or left-wing perspective, Loach switch to directing for the cinema. His prolific output includes Kes, Family Life, Riff-Raff, Land and Freedom, The Wind that Shakes the Barley, and I, Daniel Blake. The latter, released in 2016, is a savage exposure of life on benefits under the present Tory Government. It won the prestigious Palme d’Or at the Cannes Film Festival and the 2017 Bafta Award for Outstanding British Film.

In the face of this extraordinary creative history, it seems rather amazing that the Labour Party has parted company with Loach. And why now and not 10 or 20 or 30 years ago? Why not when Loach filmed a deliciously wicked “fly on the wall” documentary of the 1983 Labour conference, when garrulous the Neil Kinnock was elected leader? In fact, the Labour leadership was happy to have Loach as a member for three decades till he left in the 1990s (as did I) in disgust at the rise of Tony Blair.

Loach rejoined Labour when Jeremy Corbyn became leader in 2015, sensing the party had returned to its radical roots. Certainly, Loach was associated with the Trotskyist far left in his youth. But then, Keir Starmer was actually a member of the Trotskyist International Revolutionary Marxist Tendency during his Oxford days.

INCIDENTALLY, Ken Loach is also an Oxford graduate plus has an honorary doctorate in civil law from the university. Starmer only has a bachelor’s in civil law. Loach has another five honorary doctorates including from our own Heriot-Watt.

True, Starmer has a knighthood. But then Ken turned down an OBE in 1977. He explained: “It’s all the things I think are despicable: patronage, deferring to the monarchy and the name of the British empire, which is a monument of exploitation and conquest. I turned down the OBE because it’s not a club you want to join when you look at the villains who’ve got it.”

What radical party worth its name would keep Keir Starmer as its leader while expelling an artist and passionate reformer like Ken Loach? Back in 1962, future prime minister Harold Wilson told Labour’s annual conference: “This party is a moral crusade, or it is nothing”. Coming from the uber-pragmatic Wilson, that set quite a test – though a correct one. Kicking out Ken Loach proves contemporary Labour is no longer a moral crusade. Or any kind of crusade, come to think of it. Under Starmer, the have descended to being a grubby political machine desperate to find a set of policies – any policies – to get themselves back into the ministerial limos.

Politics should be a moral crusade otherwise its practitioners will become mere opportunists. That goes for any party, be it Labour or the SNP. Some will reject this notion, arguing that an exclusive ideology reduces the possibility of building an electoral coalition wide enough to win power.

But I’m not talking about a rigid ideology. I’m talking about having a set of transcendental goals that mobilise the people while setting moral boundaries on what politicians get up to. By kicking out its socialists and radicals, Starmer’s vacuous party machine has neutered itself politically – ensuring it will never be elected again.

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If ever there was a reason to support Scottish independence it is the dawning realisation that the incompetent, corrupt Tories are likely not only to win the next General Election, but the one after that as well. The more Starmer tries to ape the Tories, the better chance the electorate will vote (and vote again) for the real thing. A Labour Party serious about winning power would hire Ken Loach to produce its campaign commercials – not expel him.

There are lessons to be learned in Scotland from this episode. The SNP have had a long, factious relationship with its poets and artists. Hugh MacDiarmid was a founder member but left to join the Communist Party. But the whole point about poets – in word or celluloid – is that they have the dispensation to imagine a better world. You cannot have a genuine political crusade without poets.

Alas, the Scottish national movement is in danger of being reduced to a dull political machine rather than a moral crusade. Policy is made by focus groups and special advisers. Vision has been replaced by risk aversion. The likes of Hugh MacDiarmid, Hamish Henderson and Compton Mackenzie must be turning in their graves.

The thing about poets, though, is that they tend to get the last word. I suspect Sir Keir Starmer is never destined to see the inside of Number 10. But Ken Loach’s films will still be being watched 100 years from now. Hopefully Cathy will be home by then.