I didn’t think we’d get here quite so soon but we’re now at the stage in the general election campaign where the Prime Minister is running around promising all kinds of things in the knowledge he will never have to deliver them. Free cake for everyone on Thursdays! Free umbrellas for anyone caught in the rain! The Rwanda flights will take off very soon! No one believes a word of it.

But I wonder if, in his desperation, Rishi Sunak has actually stumbled on a good policy: national service. We know why he’s saying it: he thinks mentioning the idea could shore up the votes of major-generals in Chipping-Wolton-on-the-Wold who believe a spell in the army would sort most things out. National service is also a very popular idea with people who are well over the age where they might actually, God forbid, have to do it themselves.

But let’s give the Prime Minister a hearing because there could be something good in national service (fyi: I’m also well over the age where I might actually, God forbid, have to do it myself so that’s all good). It’s also not the first time the concept has been mentioned: David Cameron was banging on about it when he was PM and even Jack McConnell, while he was First Minister, suggested a kind of national service run by the Territorial Army. It’s something that comes up quite a bit.

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Part of the problem though is that whenever it does come up, we instantly get visions of what we think national service is: people who look like Charles Hawtrey being yelled at by people who look like Windsor Davies. Admittedly, there might have been some truth in it at one point but it’s based on national service as it was from the 1940s until the 1960s, and that’s quite a long time ago now. Anyone who went through it would now be in their 80s at least.

And the concept the Tories have come up with is quite different. What they’re suggesting is that 18-year-olds would be given the choice of either joining the military full-time for a year or volunteering one weekend every month for community organisations such as the fire service or the police. The Prime Minister said it would help young people to "learn real world skills, do new things and contribute to their community and our country”.

But the really important part is that it would be compulsory. When Jack McConnell was talking about national service with the TA, there was never any suggestion people would be forced to do it. David Cameron also went ahead and set up England’s National Citizen Service which puts 16 and 17-year-olds through a spell of community work, but again it’s voluntary. The young ones don’t have to do it so, on the whole, most of them don’t.

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For those that do, the results are good. Research by Ipsos Mori into the National Citizen Service showed people who took part left with improved confidence and interpersonal skills. The same applies to Scotland’s “I Will” movement, which is run by Youth Link Scotland and aims to encourage young people to take part in volunteering and community work and sees good results when they do. In a way, there’s no argument over the basics: kids who take part in community work usually get a lot out of it.

It's the same with any kind of military service. I remember spending the day on HMS Ark Royal while the aircraft carrier was docked at Loch Long and speaking to the young members of the crew who, one after another, spoke about how they’d been changed for the better by the Navy. I also spent a bit of time with troops in Afghanistan and, again, there were lots of soldiers who credited military service with improving their lives or saving them from lives that might have ended in trouble.

Of course, all those men and women in the military had volunteered (albeit some may have felt various kinds of pressure to join up, from family say). The people who do the National Citizen Service and similar schemes are also volunteers and are likely to be the kind of shiny-faced middle-class kids who do Duke of Edinburgh (not that there’s anything wrong with shiny-faced middle-class kids who do Duke of Edinburgh – I was one once). The point is they’re not actually the people who get the most out of it.

The ones who do get the most out of it – and I’ve seen it mostly with the military – are kids from more deprived circumstances. The research Ipsos Mori did into the National Citizen Service for example shows that it was young people from the poorest backgrounds who showed the greatest improvements by taking part, but they were also much less prone to volunteer. In other words, the kids most likely to benefit are the least likely to take part.

The Tories seem to get this with their version of national service. In announcing it, the PM spraffed on about pride in our country which is hot air during an election really; more important is the fact that their scheme would reach all 18-year-olds, including those from more deprived backgrounds and those who may be unemployed or out of education: the kids least likely to take part and the most likely to benefit. That is why, for it to work, it needs to be compulsory.

One of the surprising things is that you’d think the idea of making national service compulsory would be supported mainly by the major-generals in Chipping-Wolton-on-the-Wold and certainly not by the 18-year-olds themselves. But an opinion poll conducted by the think tank Onward found that three times as many people aged 16 to 21 support national service than oppose it. They know what’s good for them, you might say. It’s also worth noting that national service isn’t just a right-wing thing: it’s already in place in liberal democracies such as Sweden and Norway and works well.

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Of course, all this talk is theoretical for now because the Tories aren’t going to win the election and therefore won’t have the opportunity to put their plan into action (and they may have suggested it in the first place because they know this). But it’s certainly worth talking about. The Labour leader Sir Keir Starmer said the other day that he’s minded to give 16 and 17-year-olds the vote: “If you can work, if you can pay tax, if you can serve in your armed forces, then you ought to be able to vote,” he said.

But it works both ways doesn’t it? Sir Keir says the responsibilities people have, such as the responsibility to get a job or to pay tax, should come with rights such as voting in elections; fair enough, absolutely. But we should also talk about what kind of responsibilities come with the rights and, even though I am now too old and will never have to do it myself and that might be unfair, one of the responsibilities could be to give a year of service to a military or civil organisation. We know it would be good for the organisations, because all of them are chronically short-staffed. But more importantly, it would mostly be good for the people who do it.