At the heart of the debate around legal migration are contested notions of fairness. Home Secretary Shabana Mahmood has talked of her parents coming to the UK from rural Kashmir. Now, this daughter of immigrants is responsible for reshaping the very system that brought them here decades ago – and doing so in a way that both her party and the country regard as fair.

"Fair to those who seek a new and better life here, like my parents did. And fair to those already here, including British workers, and especially the young," is how Mahmood put it in her speech to the Labour Party conference in September.

The debate has come at a time of huge legal immigration in recent years and during a period in which Reform UK have been particularly prominent in the national political conversation.

Both of these things are factors in Labour wanting to be seen to be taking people's concerns about the scale of arrivals seriously.

But her political opponents smell what they see as weakness and retreat, with parts of her original plan now being revised, as the BBC's Iain Watson reported over the weekend.

It is worth examining this policy throughout the last year or so, as it is instructive in how we have arrived at today's announcement.

In November last year, Mahmood set out a plan called "a fairer pathway to settlement". The idea was opinions on her instincts would be sought in a consultation. And boy, were their plenty of opinions offered.

Around 200,000 people contributed to the consultation, of which 140,000 responses came from visa holders themselves I'm told.

"It's been a colossal exercise and a genuine one," is how one Whitehall source put it to me, claiming: "We have taken the time to get this right." Or is the real truth that they have buckled under political pressure from their own side – and a change of prime minister?

Mahmood said last year that she felt compelled to act because "between 2021 and 2024, we have seen net migration of an additional 2.6 million people. Around one in every 30 people in this country today arrived in these four years." It is what critics have labelled "the Boriswave", named for the changes made under former Prime Minister Boris Johnson.

And, Mahmood argued, it was important to act with urgency, as very soon significant numbers of those recent arrivals would start qualifying for indefinite leave to remain, or ILR.

"Migrants on lower wages who bring non-working dependants and children are likely to present significant fiscal costs to the UK.

"It is therefore right that we apply more stringent controls for this group before they qualify for settled status," she said, adding: "Under our current rules, they will usually qualify for benefits payments and council housing five years after arrival.

"As the majority of this group began arriving from 2022 onwards, this is currently set to begin in 2027. We consult here on a separate baseline qualifying period, of 15 years, for this group." But plenty within the Labour Party and beyond were uncomfortable – and yes, they cited fairness, or the perceived lack of it, in mounting their criticisms.

As the now Housing Secretary Angela Rayner put it in March, before she returned to government, the ideas were "un-British" because they involved "moving the goalposts" - migrants who had arrived in good faith under one set of rules would have their future in the UK determined by the new ones.

Just a few weeks before Rayner's intervention, Mahmood had doubled down on her plans. Addressing the centre left IPPR think tank, she said "in just four years, this country experienced levels of migration it had previously seen across four decades.

"It was not just the scale, but also the nature of that change that was so destabilising." There was more, and with a big number attached.

"We have never, in the history of this country, had so much low-skilled migration in so little time.

"We estimate, based on findings from the Migration Advisory Committee, that the lifetime cost to the taxpayer will be £10bn. That figure would be paid for by working people in this country."

She added: "It is an affront to the idea of fairness within our migration system." Incidentally, the £10bn figure is contested by some – or at least placed in a wider context.

The aforementioned IPPR argue that the original plans were "never in reality going to create a £10bn long-term saving, given they were meant to delay care workers' eligibility for ILR rather than prevent them from settling altogether.

"Delaying ILR would save money on welfare, whereas the £10bn figure includes much broader long run costs once care workers enter retirement, claim the state pension, and make greater use of health and social care." Nonetheless, Mahmood's message in March left senior Conservatives privately agreeing with her – and struck by her willingness to be unflinching in her approach to the subject.

But around 100 of her Labour colleagues were not happy – and making their views known publicly.

He told me it was important to "work hard to get the balance right" but that the "broad thrust" of what the home secretary was doing "is right".

"Broad thrust" will be the words that account for the gap between what Mahmood used to say and what she is saying today.

The Conservatives and others will seize upon the change. The Tories will argue it amounts to an "excruciating U-turn" as one senior figure described it to me, claiming it would be "deeply personally embarrassing" for the home secretary.

They also ponder how the government will choose to make the changes, as they believe if primary legislation isn't used to do it – such as via an amendment to the Immigration and Asylum Bill currently before parliament – the plans could be successfully challenged in court.

Mahmood will argue she has tried to finally arrive at a policy the widest range of people may see as fair. We will see and hear the range of reaction she provokes in the coming hours and days.