will try to draw a line under the era today as he declares winning the next election is more important than left-wing dogma.

In his first in-person Labour conference speech, Sir Keir will vow that under his leadership the party is ‘back in business’ and focussed on pragmatic play solutions for Britain’s problems. 

Aides said Sir Keir will use his biggest political moment yet to promise to recruit thousands more teachers, and call for improvements to mental health care.

He is also expected to mount an effort to rehabilitate Labour’s reputation for managing the public finances, as well as committing to creating a greener economy. 

But the leadership’s main aim is to show voters the party has changed since Mr Corbyn – at that time backed by Sir Keir – led it to electoral catastrophe in 2019.

Shadow cabinet members privately accept that SIr Keir has an almost impossible task to overturn Boris Johnson’s 80-strong majority in a single election.

They are already urging him to cling on if he loses the poll but manages to make significant progress against the ‘popular’ PM. 

‘No politician stays popular forever,’ one frontbencher told MailOnline of Mr Johnson. ‘He’s been through a whole list of scandals which would have killed any other politician’s career and I think a tipping point will come when people look at him and decide they don’t like what they see.’ 

Positioning Labour as a credible government-in-waiting, Sir Keir will tell supporters: ‘Too often in the history of this party our dream of the good society falls foul of the belief that we will not run a strong economy.

‘But you don’t get one without the other.And under my leadership we are committed to both. I can promise you that under my leadership Labour will be back in business. 

A source said the hour-long speech, which will be his most personal to date, will be ‘noticeably different from what you’ve heard from Labour in recent years’ and will be ‘more optimistic, more focused on the future, more outward looking’.

‘It will be a clear indication that Labour will never again go into an election with a manifesto that isn’t a serious plan for government,’ the insider added.

Trying to capitalise on the current fuel crisis, Sir Keir will describe the Government as ‘lost in the woods’.

In a round of interviews this morning, Justice Secretary David Lammy said Sir Keir had proved this week – amid spats with the hard-Left and one resignation from his senior team 0 that he is a ‘fighter’.   

‘The road may have been a bit bumpy at points but he has come out, as cool as a cucumber, and as a fighter,’ he told Times Radio.

Sir Keir was someone with ‘compassion and kindness running through him’ and he is ‘in touch with suburban Britain’, he said.

In a series of policy announcements, Sir Keir will say Labour would guarantee access to mental health treatment in less than a month. 

The party would create a National Excellence Programme for education, and recruit more teachers to enhance the prospects of the 40 per cent of young people who leave compulsory education without essential qualifications. 

Mr Lammy said the party will not make the same ‘mistake’ as Mr Corbyn by endlessly splashing cash without explaining where it is coming from.

‘We will not be making proposals that cannot be costed, the public need to know where the money is coming from.

‘Clearly it was the case at the last general election, we were coming up with policies like free broadband, policies on pensions for women, a four-day week, and the public were saying ‘how much is this going to cost’?

‘It was coming at the last minute, they felt confused and they didn’t feel able to trust us because of some of the issues that were dominating the party.’

He believes voters who had given Mr Johnson the benefit of the doubt are now concerned about his competence.

<div class="art-ins mol-factbox news halfRHS" data-version="2" id="mol-47af9d20-20ba-11ec-829f-dfdabd72ee00" website kills off Corbyn era in first real Labour conference speech