A glottal Glaswegian gets unnerved on first encountering Joanna Cherry: she is so well-spoken. Immediately you find your grammar sitting up straight and paying attention and your slovenly syntax tucking its shirt back in. Those consonants you keep losing in the middle of sentences start returning and your cosy profanities all flee.

Cherry has announced her intention to seek her party’s nomination to represent Edinburgh Central at next year’s Holyrood election and I’m here to ask her why. After all, she has just been returned to Westminster where she increased her majority massively in Edinburgh South West. Why now? Is Westminster, the mother of all parliaments, not enough? Her main opponent from within the party will be Angus Robertson, another erudite child of this city.

And yet, eloquent and fluent as they both are, this will be a bruising contest. Cherry and Robertson are two of the brightest and best in the party, but there seems no love lost between them. The contest hasn’t even started yet – the window for further nominations is still open – and Robertson has already had a swipe at his party colleague about empire-building. She has returned this with interest amidst disguised references to Robertson’s carelessness in losing his Moray seat to a Tory in 2017.

A state of civil strife quietly thrums beneath the surface of this most disciplined of political machines, and Cherry and Robertson are seen to be on either side of the fault-line. Allies of Cherry feel Robertson’s fingerprints are all over some of the moves that have been made against her within the Westminster group over the last year or so.

Cherry, currently the MP for Edinburgh South West, has become one of the most recognised parliamentarians at Westminster since she won her seat in 2015, feared and admired in equal measure. She was instrumental in defeating Boris Johnson’s plan to sabotage parliament late last year and is a formidable speaker from the floor of the House. This has caused jealousy among lesser-plumed party colleagues who have dutifully toiled in the party for years without any recognition. “She’s just in the door five minutes,” they say, “and already she’s coveting Nicola’s job. That’s the real reason why she wants to run for Holyrood.”

“So, do you really want the First Minister’s job,” I ask her. We’re sitting in a tidy constituency office in Edinburgh’s Jam Tarts district. I’ve just told her that if she wants to continue to do well here she should walk into the Tynecastle Arms and sing the famous old Hearts song: “Aye, Aye, Aye: Cruikshank is better than Yashin; Busby is better than Eu-se-bio; the Hibees are in for a thrashin’.” I’m hoping to catch her off-guard when I ask her the big Nicola Sturgeon question.

READ MORE: Scathing complaints accuse SNP MP Joanna Cherry of 'making party look regressive'

“I don’t want to replace Nicola; I want to get to know her better,” she says. “But the pair of you can hardly stand to be in the same room as each other,” I say. “That’s just idle speculation,” she replies. “Nicola and I have so much in common; we both studied law; we’re passionate feminists and passionate about reducing inequality.

“Whenever I’m in other parts of the UK I’m told how much they admire Nicola and wish they could have someone as good as her in English politics. I’m proud of her and of how well she’s represented the cause of Scottish independence. I want to support her in leading Scotland to independence and in securing our return to the European Union. I certainly have my differences with her, not least on her support for the proposed reforms of the Gender recognition Act, but more unites us than divides us.”

Ah yes, the Gender Recognition Act: never has something so scarcely understood by the vast majority of the general population caused so much turbulence within the gilded chambers of a political party. For those who inhabit the world outside cyberspace and the political bubble this is what it means. The Scottish Government wants to make it much easier for people to change their gender by enabling them to "self-declare" rather than endure a prolonged process. Cherry and other feminists within the SNP, most notably Joan McAlpine, convenor of Holyrood’s influential Culture, Tourism, Europe and External Affairs Committee, have urged caution.

HeraldScotland:

Both women have endured abuse and intimidation from within the party for expressing concerns for women’s sex-based rights if the proposed GRA reforms come to pass. Cherry is careful to say that the abuse has come from “the tiniest of factions” who wield “disproportionate influence”.

“As an out gay woman who fought section 28 and has campaigned for LGBT rights for decades, accusations that I am transphobic are offensive. The online abuse does take its toll but I am more worried about the cumulative and detrimental effect on what it does for the role of women in politics and in the media; young women in particular. I don’t like the way this is characterised as a problem in the youth wing of the party.

READ MORE: MP Joanna Cherry: Scotland will be ignored at Westminster

“Many admirable young people are involved in Scottish politics and I know a number of women and men in Young Scots for Independence and SNP Youth who have spoken to me privately about their concerns. The abuse is deeply misogynistic. The attacks on me and other women in the party are clearly a breach of our code of conduct and must be dealt with.

“I’m very proud of the fact that in Scotland we have very good rights-based protections for trans people. No one is seeking to change that. However, women have legitimate concerns about the proposed changes to the law on gender recognition.”

Within the SNP’s Westminster group you sense she is admired rather than loved and there’s not a little resentment at her high profile. One of her party colleagues at Holyrood has been aghast at her treatment at Westminster: “She’s a really sharp intellect, as forensic in her approach to politics as she was to the law. She does have what Burns called 'a guid conceit o hersel'. This is admired and expected in male leaders, but women are held to a different standard and expected to show humility. She needs to build alliances though; that is the clubby bit of politics which can evade hard-working women and allow mediocre men to advance.”

Cherry challenges my suggestion that the party could do without this contest in Edinburgh Central. “Competition in politics is healthy,” she says. “Debating ideas is good for developing policy. This isn’t being disloyal to the leadership. Holyrood and Westminster proceed by debate; this is how we get to the nub of things.”

The fabled independence Plan B, which the party rejected last year, has returned for inspection now that Boris Johnson simply won’t discuss a second independence referendum. This is another area where Cherry is perceived to be at odds with her boss. She rejects this.

“I wouldn’t back a wildcat or illegal referendum. How could I, given my legal background? I endorse Nicola’s declaration that this should proceed legally. However we have reached an impasse: people keep voting for us and opinion polls show support for Yes is hovering around 50%, yet Johnson won’t budge.

“My experience of knocking on doors is that there are lots of soft Nos who are interested in the idea of Scotland staying in the EU through independence. But we have to look at the economy and currency; the process of getting back into the EU and how long’s it going to take. We must also deal with the border with England and de-dramatise it. The idea that people won’t be able to have a cup of tea in Berwick without showing their passport is ludicrous. We’re all in the common travel area."

Cherry is keen to stress that seeking a ruling from the Supreme Court on Holyrood’s competence to hold a referendum without London’s agreement does not amount to support for a wildcat vote.

"If we pass a bill through Holyrood to hold a referendum this might be challenged by the UK government’s law officer and then arrive at the Supreme Court. Any organisation could challenge it. Under section 33 of the Scotland Act within four weeks of a Bill passing the Advocate General, the Attorney General or the Scotland’s Lord Advocate could choose to refer the question of the Bill’s competence to the Supreme Court.

“It would be for them to decide by a process of statutory interpretation whether this Bill was within the powers of Holyrood. I’d hope they wouldn’t just look at the Act but note the two countries’ markedly different routes of travel and all the recent democratic votes in several political jurisdictions. If they said the Bill was within Holyrood’s competence we’d have our referendum. And if not I don’t think we’d lose anything.”

Cherry would probably have been a judge by now if she’d continued her legal career, with the prospect of earning much more money. She had a stellar career specialising in prosecuting sexual offence cases. Why did she choose this uncertain and venomous arena where party rules can’t prevent a woman from experiencing abuse and venom simply for adhering to long-held principles?

“If I’d known it would be like this I wouldn’t have stood for election,” she says, “and it’s sad that women might be put off entering politics because of it. And I don’t think I’ve had the support I should have had through all of this.

“But we’re now at the end game for Scottish independence and the focus is on Holyrood. I want to be part of it. Independence for Scotland has been my lifelong passion.”