"That's not how we work in the Labour Party."

Thus spake deputy leader Angela Rayner when asked whether the party's candidate for Rutherglen & Hamilton West, Michael Shanks, would be suspended by the party in the event he voted against a three-line whip on the two-child benefit cap.

She continued: "Obviously if backbench MPs vote against the whip then... they do do that from time to time and they have done that.

"He wouldn't be the first Labour MP to vote against a vote we've had in parliament. He will be the voice of the people that he's there to represent and I understand that."

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In the event Mr Shanks, who was elected in the by-election and re-elected in the general election a few months later, did not vote against the new government.

Seven of his parliamentary colleagues did, however, and were promptly suspended for six months as punishment.

An SNP amendment to the King's speech calling for the cap to be abolished was defeated by 363 votes to 103, but was backed by Labour's former shadow chancellor John McDonnell, as well as Richard Burgon, Ian Byrne, Rebecca Long-Bailey, Imran Hussain, Apsana Begum and Zarah Sultana.

As rebellions go it was rather a small one, but its implications may go far beyond the numbers, both at Westminster and in the upcoming Scottish Parliament election.

The two-child benefit cap came into force on April 5 2017. The brainchild of George Osborne, it prevents parents from claiming child tax credit or universal credit for a third child, and any subsequent, if they were born after that date.

According to the Institute for Fiscal Studies, it currently affects two million children and will encompass close to 700,000 more by the end of the current parliament, with campaigners saying its removal could lift 300,000 out of poverty.

The new Labour government agrees, in principle, with its removal but says the state of the public finances means it cannot until economic growth has been achieved.

Newly-elected MP Josh Simons, formerly the head of the Starmerite think tank Labour Together, said in a BBC interview: "It breaks our hearts that we can’t, but the public finances are in a dire state and we can’t commit to doing this now”.

Estimates on how much it would cost to remove the cap vary - the Child Poverty Action Group puts it around £1.7bn while Labour has estimated it would be more like £3bn.

A raft of amendments to the King's speech - including one by the previous Labour leader, Jeremy Corbyn - were submitted to force a vote on the issue. The SNP's was selected, and it put Sir Keir Starmer on an early collision course with the left of his party.

With the possible exception of his father having been a toolmaker, the new Prime Minister's most repeated phrase is surely "changed Labour Party".

The 2019 election, under the leadership of Mr Corbyn, saw the party lose 60 seats at Westminster including many in its traditional 'Red Wall' in the north of England.

Quite who was to blame for this probably depends on your political persuasion. For many the MP for Islington North was simply unelectable, a nightmare on the doorsteps due to his socialist views. Others would suggest the party's inability to take a coherent stance on Brexit, torn between the Red Wall and the big cities, was its downfall.

Mr Starmer falls very much into the former camp and, following his election as leader, moved swiftly to shift the party away from Corbynism.

In the years running up to the 2024 general election the party dropped plans to abolish the charity status of private schools - though it will now levy VAT on fees - ditched a pledge to abolish tuition fees, abandoned plans to raise income tax on the top 5% of earners and scaled back nationalisation plans to include only the rail network.

Mr Corbyn himself was removed. Initially suspended after saying antisemitism in the party was "dramatically overstated for political reasons by our opponents inside and outside the party", he was barred from standing as a candidate for Islington North then expelled when he announced he'd run as an independent. He would go on to hold the seat at the general election.

In the months leading up to the general election Mr Starmer was forced to deny he was executing a "purge" of the more left-wing elements of his party.

Faiza Shaheen was deselected as the Labour candidate for Chingford and Woodford Green, Lloyd Russell-Moyle after a complaint he called "vexatious and politically motivated", and Dianne Abbot initially appeared to have been deselected before being allowed to run.

Starmer allies such as Luke Akehurst and Mr Simons, who once suggested people smugglers should be shipped on a barge to the north of Scotland, were selected for safe seats.

Ms Shaheen ran as an independent and both she and the Labour candidate took over 25% of the vote, allowing Ian Duncan Smith to hang on as an MP due to the split.

Perhaps the final fight with the left of his party is the two-child cap.

In February 2020, during his leadership campaign, Mr Starmer said: "We must scrap the inhuman Work Capability Assessments and private provision of disability assessments (e.g. ATOS), scrap punitive sanctions, two-child limit and benefits cap."

When it came to the SNP amendment though, it was made clear party unity would come above all.

Kim Johnson, the MP for Liverpool Riverside, had proposed her own amendment but voted with the government "for unity", while the seven rebels faced a six month suspension.

For some centrist commentators, it wasn't really about the benefit cap. Though calling the response "excessive", the liberal columnist Ian Dunt described the vote as "a pointless theatrical display of look-at-me conscience from the rebels", while author Tan Smith said it wasn't "even about the child cap for those Corbynite Labour MPs, I think it was about martyring themselves".

Jonathan Ashworth, a former MP and Mr Simons' replacement as head of the Labour Together think tank, defended the move to remove the whip in a radio interview, with Ms Sultana pointing out he had been an opponent of the two-child cap when in parliament.

The BBC's political editor Chris Mason described the suspensions as a "ruthless display" of Mr Starmer's power against some of the "leading faces and voices of Jeremy Corbyn’s shadow cabinet". For his part, the former leader called the decision "shameful".

Whether or not it's a final victory, however, could come down to Scotland.

(Image: Newsquest)

The Scottish Labour leader, Anas Sarwar, has called the cap "wrong", saying reversing it would be like "pushing on an open door". Mr Shanks described it as "heinous" and said he would vote against, but in the event none of Labour's MPs in Scotland did so.

With a Holyrood election in 2026 in which Mr Sarwar will hope to make significant gains and, ultimately, become First Minister it's a clear line of attack for the SNP.

On a visit to Edinburgh days after the election, Mr Starmer declared "Scotland is back at the beating heart of my government", with much of the general election messaging focusing on being able to actually influence government policy rather than being in perpetual opposition like the SNP.

Ahead of Tuesday's vote on his amendment, the SNP's Westminster leader Stephen Flynn hammered home the message about child poverty and urged those on the Labour benches to vote against the government, while pointing to Holyrood's child payment as a potential mitigation against child poverty.

If Mr Sarwar is to beat the 'branch office' allegations, he'll have to have something tangible to show when asked why a policy Scottish Labour opposes was kept in place in the name of unity with the central party.

Mr Starmer has said he will look to scrap the cap when it's fiscally prudent to do so, and the run-up to 2026 would seem politically expedient too.

Cold comfort, you'd say, for the 300,000 children who were not lifted out of poverty and, even if memories are short, likely to raise questions over why he suspended the seven who voted to do so.