Jo Swinson won’t be our next prime minister but her election campaign has achieved one significant thing already: she’s helped the BBC to start doing the job of journalism on trans rights issues.

The Lib Dems have taken a conscious decision to go into the election campaign as the party of trans rights and inclusion. They think that embracing the transgender issue plays well with the degree-educated, socially liberal voters in university towns.

I can’t judge how well the Lib Dem trans strategy is playing out with those key voters. I can simply assess the public results of that decision, which has been a string of frankly horrible broadcast interviews by Swinson and other Lib Dem candidates. This morning saw another such horror when Swinson went on BBC Radio 4’s Today programme and was asked by Justin Webb if she accepted that 'biological sex exists' and that people are therefore either male or female.

Her answer: 'Not on a binary.'

She then talked nonsense about chromosomes and chucked around some scientifically illiterate babble and talked about 'cisgendered women' before declaring: 'This is not a scientific debate.'

Which is actually true. It’s a debate about law and policy and politics and one that too many people have avoided because of the extraordinary levels of vitriol involved. Because some of the actors are very, very keen to avoid public scrutiny or discussion.

I have written before about how the BBC has sometimes failed to cover the trans issue properly, or even at all. Some BBC output has been hopelessly lacking in basic critical analysis. Sometimes the corporation has simply ignored matters of real public interest.

There are lots of reasons for this, but I don’t fault individual BBC journalists. The corporation employs some very good journalists who have long been keen to do their jobs and scrutinise this issue as they would any other, but who have not always been able to do so in a corporate and editorial culture that has sometimes discouraged such acts of journalism.

But in the last ten days, the Lib Dem enthusiasm for trans issues has helped the BBC get over its squeamishness and see that when politicians propose to change the law in ways that might affect the rights and experiences of different groups of people, it is the job of journalism to ask questions.

So last week saw Emily Maitlis on Newsnight asking Sarah Wollaston some sharp questions about how a policy of recognising 'self-identified' gender in law would interact with services legally segregated on the basis of sex. And Emma Barnett likewise filleted Swinson on Woman’s Hour, a programme that has a somewhat chequered record on these issues.

Maitlis and Barnett are two of the stars of BBC journalism, deserving of all the praise they get for their interviews with politicians on other things (declaration: Barnett is my former colleague at the Telegraph. But honestly, I’d still say she was brilliant even if I didn’t know and like her). The fact that big-name interviewers have marched into this issue and treated it like any other, asking questions and testing politicians’ claims, is hugely important.

When I started writing about this topic nearly two years ago, it was in part out of frustration that it wasn’t being treated as a 'normal' subject of journalistic inquiry. At the time, quite a few journalistic friends got in touch to say I was being 'brave' to tackle the issue and to explain that they could or would not be following suit because, well, reasons.

Today I see signs that the climate has shifted. It is becoming normal and safe to talk about this stuff, to ask questions. Even awkward and uncomfortable ones. On Today, Justin Webb asked Swinson about the simple reality that a person with male anatomy is different to a person with female anatomy and that the potential interaction between those two sorts of bodies ought to be governed by rules that recognise those differences and that potential.

He said to her: 'I could do you enormous damage because of my male body. That is a fact.'

He’s right, of course. A physical male poses a potential threat that a physical female does not. A person with a penis can do things to other people that a person without a penis cannot. This is already recognised in law, incidentally: English law defines rape as unwanted penetration with a penis. And this is what a lot of the trans debate boils down to.

Transgenderism says that a person with a penis is a woman if they say they are a woman. 'Trans women are women' means people with penises have the same legal right to enter 'women-only' spaces (changing rooms, refuges, prisons) as any other woman – simply on the basis of their self-declared gender. That raises the question: do other women, women who don’t have penises, have the right to say 'I do not wish to share intimate spaces with a person who has a penis'?

Yet for understandable reasons of decorum and good manners, a lot of people don’t want to address these basic facts of the debate. Really, I’m not wild about it myself. If you’d asked me a couple of years ago to set out my limited journalistic ambitions, using the word 'penis' repeatedly in The Spectator would not have topped the list.

I certainly can’t imagine having the guts to put to a female politician, live on a flagship BBC programme, the blunt truth that my male body means I pose a potential threat to her that someone with a female body does not. Yet that’s the sort of unflinching honesty this debate needs, and I think Justin Webb should be applauded for that interview this morning.

Jo Swinson should be applauded too. She may not have meant to, but she’s helped the BBC do some proper journalism on an issue that has been kept out of the spotlight for too long. Most voters are still largely in the dark on this issue, but with every interview, every broadcast, more of the public will come to see that there are questions about the trans rights agenda which must be asked and which remain unanswered.