IT seems almost indecent to intrude on private grief but Labour leader Jeremy Corbyn’s botched relaunch this week demonstrates that it isn’t easy to be a populist. It’s not just that you need to get your policies sorted, unlike his self-imploding initiatives on free movement and capping top pay. Donald Trump never bothers about policy coherence or even truth. You have to tap into something visceral, something emotional, and not care what the media says.

The first mistake was to trail in advance that the Labour leader was going to turn “populist” in the New Year and hook into the “insurgent” rebellion against the establishment that’s running rampant across the developed world. I’m not exactly sure who inspired this media strategy, but it was so widely reported that it clearly came from Mr Corbyn’s office. It was a colossal own goal.

It invited cartoonists to pen images of Mr Corbyn wearing a red “Make Britain Great Again” baseball hat a la Mr Trump. Why was Labour inviting comparisons between its mild-mannered, left-wing leader and right-wing populists? It didn’t mean to suggest that Mr Corbyn was similar in policy terms to figures like Mr Trump, Marine le Pen or Nigel Farage but it sounded as if he was.

As for being populist, surely the rule, like being cool, is to show not tell. There’s nothing worse than an uncool person, like your dad, saying how cool he’ll be when he gets his new car. Also, if you have to tell people you are a visceral, charismatic populist, you aren’t one. You don’t hear Mr Trump telling people how anti-establishment and transgressive he is; how he is in touch with the feelings of the marginal, white “left-behinds” in rust-belt states. He shows it by staging mass rallies across America at which his anti-liberal, anti-immigrant rants are like the deplorables’ version of a Bruce Springsteen concert.

Mr Corbyn’s people could learn from the king of left-wing rock. Springsteen’s followers often describe his shows as being like a church service; a raucous one involving a dialogue between the boss and his congregation about highly moral issues like unemployment and Iraq. Songs such as The Ghost of Tom Joad are some of the greatest anti-capitalist anthems around, even though penned by a plutocrat who’s worth $460 million (according to Forbes) and who earned $60m last year.

I’m not suggesting Labour gives its leader a guitar and turns him into a rock god. But emotion is one of the strongest bonding agents between a leader and his following. Springsteen is a mass of contradictions: a left-wing internationalist who is careful to nurture his base by lacing his songs with patriotism. Born in the USA was adopted as a campaign theme by Ronald Reagan (even though it’s actually about Vietnam). We Take Care of Our Own (wherever this flag’s flown) is the mission statement of the US marines. Springsteen’s songs are a celebration of the American way of life, about cars and girls and working in construction. In some ways, the Boss is as nationalist as Donald Trump.

Springsteen is living proof that the idea of setting a limit to top pay is unworkable. Who will decide what the ceiling should be for footballers and rock stars? Much better to let them accumulate wealth and tax it fairly. A 60 per cent top rate would be a starting point. When American capitalism really was great, in the 1950s and 60s Springsteen’s music evokes, top tax rates were more than 80 per cent.

Mr Corbyn couldn’t be more different in style but Labour needs an emotional resonance to its politics, a form of British nationalism, to act as a new bonding agent between the party and the country. Nationalism was always a key part of Labour’s appeal in the past. Clement Atlee deployed the sense of national solidarity that lingered after the Second World War to create the New Jerusalem of the welfare state.

It isn’t called the National Health Service for nothing. The concept of national solidarity was used to provide the momentum for the greatest socialisation of a developed industrial economy ever achieved in peacetime. You can only justify the redistribution of wealth when there is a higher moral purpose: bringing the nation together.

Socialism and nationalism can go hand in hand; indeed, democracy and nationalism are closely aligned historically. This brings us to the other great exemplar of social democratic populism: Nicola Sturgeon. The wave of insurgent populism arguably began in Scotland in 2014.

I’ll sidestep the issue of just how socialist the Scottish Government is in practice and take it as read that the SNP achieved political hegemony in Scotland not by national chauvinism and hatred of English people,but by wedding a powerful sense of national awakening to social democratic themes. It was the SNP’s opposition to austerity, tuition fees, NHS privatisation, welfare cuts and foreign wars that inspired the Yes Campaign to unite behind its nationalism.

The SNP even made internationalism part of a nationalist agenda. While Labour has tied itself up in impossible contradictions over its attitude to the European Union, suspecting that to be properly English you have to emulate Ukip, the SNP has made membership of the single market, and belief in free movement, a touchstone of Scottish national identity. The First Minister embraces immigration as an economic good. She’s made nationalism in Scotland synonymous with anti-racism by insisting that Scottish citizenship is about more than mere accident of birth.

She seized the Syrian refugee crisis to portray Scotland as a country that welcomes other races. Scotland took the lion’s share of asylum seekers and demonstrated that they can be peacefully integrated into society.

Nationalism should be about making a country feel good about itself. Ms Sturgeon makes Scots feel good about being Scottish by being open minded and egalitarian. It is evident in the way you hear many Scottish men boasting in London pubs about how Scotland’s three biggest parties are led by women.

The immense electoral success of the SNP is not based on nativism and ethnic exceptionalism but on opposition to right-wing politics.

What can Mr Corbyn learn from this? Well, he can abandon thoughts of emulating Ukip on immigration. He has to make England feel as positive about national solidarity as Scotland does, by making Labour part of that “New England” the musician Billy Bragg is always talking and singing about. It shouldn’t be too difficult. England is the nation that gave us popular democracy, trades unions and the welfare state.

Mr Corbyn needs to keep plugging away at this in his mass rallies, where he really does connect. He’ll never be a charismatic leader but he has built a huge following and just needs a message that resonates with people’s sense of injustice. And he needs to avoid baseball caps.