Back in 2009, Reed, as leader of Lambeth Council, had expected to be selected as the prospective Labour candidate for his then home constituency of Streatham. But Umunna came along with a more radical, left-wing prospectus than his Blairite rival, and won over local party members who had tired of the party’s dalliance with neo-liberalism.

Reed had to cool his heels until 2012, and the death of Croydon North MP Malcolm Wicks, before he could progress his own political ambitions and get elected to parliament in another safe Labour seat.

Steve Reed OBE also wants a People’s Vote, but he won’t be leaving Labour, he said today

Today, Umunna severed his links with Labour as he and six Remain-supporting MP colleagues staged a press conference in order to slate their erstwhile party leader Jeremy Corbyn while announcing that they will form an independent group in parliament.

They said they were disgusted by the party’s handling of anti-semitism and its Brexit policy. Many observers assessed that they have opted for political oblivion, but that they might do enough to split the left to ensure Tory governments for many years to come, just as happened with the SDP in the 1980s.

The MPs are:

• Umunna, the former shadow business secretary;
• Luciana Berger, MP for Liverpool Wavertree and former shadow minister for mental health;
• Gavin Shuker, MP for Luton South and former shadow international development minister;
• Angela Smith, MP for Penistone and Stocksbridge and former shadow deputy leader of the House of Commons;
• Chris Leslie, MP Nottingham East and former shadow chancellor;
• Mike Gapes, MP for Ilford South and former chair of the foreign affairs select committee; and
• Ann Coffey, MP for Stockport and former parliamentary private secretary to Alistair Darling when he was chancellor of the exchequer.

None of the seven splitters, when asked, said that they would be resigning from parliament to prompt a by-election in their constituencies because, they claimed, in 2017 when they were elected when standing on Labour’s “For the Many, Not the Few”, the electorate chose them personally, and they did not owe their positions to any party policies.

Both Umunna and Berger have recently been threatened with deselection by their CLPs, which is surely only a coincidence.

Luciana Berger looks on admiringly as Chuka Umunna makes his bid for the leadership of his Gang of Seven. Both had faced deselection threats by their local party members

Such a split has been predicted almost since Corbyn was elected Labour leader in 2015, and there had been rumours of a centrist party launch since the New Year. It had been expected that some People’s Vote-supporting Tories – the likes of Anna Soubry and Sarah Wollaston – would align themselves with the group, but in the event, that did not happen.

Among the first to reject the independent group’s premise was Reed, a leading figure from the Blairite wing of the Labour Party and, indeed, one of the plotters who tried to oust Corbyn in the “chicken coup” of 2016.

This time, Reed – himself a People’s Vote supporter – was having no truck with the undermining of the party.

On Twitter, Reed wrote, “I’m watching the seven MPs quitting the party on TV and I’m more convinced than ever that Labour, the greatest force for social change this country’s ever known, can lead Britain forward if we now come together as a party to shape the future.”

Shortly after, Reed added this: “I’ve been a member of the Labour Party for 40 years this year, and I’m looking forward to being a member for the next 40 years.”

The remark prompted one Katharine Street observer to comment, “He doesn’t look old enough.”

Steve Reed OBE signals his intention to remain a loyal member of the Labour Party

It was significant that the Twitter feed of Reed’s constituency Labour Party soon after put out a link to a code of conduct for its members when using social media, a warning for them not to direct anger or abuse at Umunna’s not-so-magnificent seven.

That appeal for social media calm was also reflected in the comments of shadow foreign secretary Emily Thornberry: “If you criticise or abuse these individuals, if you impugn their motives, and if you encourage any others to join them, you are helping them not hurting them, because you are taking your eyes off the prize and allowing our movement to be distracted and divided, which is exactly what they want.

“The only thing that anyone should do in response to the action of these MPs today is to respectfully and politely ask them a simple question: Do they intend to put up candidates in Labour-Tory marginals, and split the Labour vote?”

Indeed, Thornberry’s warning may need to be heeded in south London, where a battle to unseat Umunna at the polls could see campaign resources – and boots on the ground – diverted from Sarah Jones’s marginal Croydon Central seat to Streatham.

But Thornberry’s wise counsel seemed to be ignored by Jack Buck, Croydon Labour’s paid organiser, who during office hours was busy on his personal Twitter account sending out a series of less-than-conciliatory messages.

“If any Labour MP quits now, just as the Tory party are in the midst of their biggest crisis in a hundred years, the resulting chaos will be on them and nobody else,” Buck first wrote.

Buck, who is an elected councillor in Southwark, then added, “Being elected at any level means acting responsibly and in the interests of others not yourself.”

Buck’s next message read: “Also, prediction. If Labour MPs split off it will be a matter of days/weeks before Theresa May calls an election to try and save herself. This will be supposedly people with Labour values saving a Conservative prime minister.”

Jack Buck, the Croydon Labour group’s paid employee, was busy expressing his own views this morning about the seven splitters

And then, possibly with an eye on the imminent vacancy for a Labour Party candidate in Streatham, Buck said: “The case for open, transparent and mandatory re-selection of Labour parliamentary candidates just got made better than any grassroots campaign ever could.”

Other London Labour figures, including many who have worked in the Commons with the splitters, tended to take a more conciliatory tone.

Sadiq Khan, the Mayor of London, said it is a “desperately sad day” for Labour, but that he would being sticking with the party. “These seven MPs are all friends of mine. I served alongside them in parliament,” he wrote.

“I agree that the only way through the mess of Brexit is to give the public the final say, and that the Labour Party needs to do much more to root out the evil of anti-semitism.

“However, history clearly shows that the only way to get real change in our society – whether fighting for a public vote, tackling inequality, or ending austerity – is within the Labour Party. When the Labour Party splits it only leads to one outcome – a Tory government – and that means a hard Tory Brexit.”

“Labour now has a plan to rebuild Britain. These MPs want to take us back to the politics of the past with a back-to-the-Blair-years programme of privatisation, tax cuts for the rich and deregulation of the banks.

“They offer no concrete solutions, no new ideas and have no support amongst the public.”