Within a very short time it's become clear that the nature of the post-leadership election Labour team will mean policy shifts which soon make themselves felt in London.
The appointment of John McDonnell as shadow chancellor will do more than send tremors through the City.
It signals an immediate change in Labour policy towards aviation, guaranteeing a stance firmly opposed to a third runway at Heathrow.
The party had previously broadly accepted the independent Davies commission's recommendations of expansion at Heathrow, subject to conditions on noise and air pollution being met.
But Mr McDonnell, MP for Hayes and Harlington, is the most strident opponent of any further expansion - with a long history of protest.
New leader Jeremy Corbyn also reaffirmed as recently as July - in an interview with the BBC's Sunday Politics - his own opposition.
And Labour's new mayoral candidate Sadiq Khan broke with party policy upon being selected and said he is now opposed, in a move widely seen as trying to neutralise Zac Goldsmith, the Conservative MP for Richmond Park who has made it his signature policy.
Mr McDonnell acknowledges thousands of jobs in his constituency depend on Heathrow, but he says it's reached its limits.
On 2009 he was suspended from the House of Commons for five days after repeatedly shouting "disgrace" at then Labour Transport Secretary Geoff Hoon after a debate on the third runway.
In July this year Mr McDonnell claimed renewed Davies' proposals would lead to an unprecedented environmental protest campaign.
"We will fight with every mechanism available including political lobbying, legal action and where necessary direct action to save our homes and community," he said.
The new Labour regime's much warmer relations with the unions could have a far-reaching effect on the mood within the capital's public services.
Over the past few years it's been rare for Labour MPs to side publicly with striking Tube workers.
Even Ken Livingstone - as London's mayor - got frustrated and fell out with the RMT rail workers' union late general secretary Bob Crow.
But one of the first unions out of the blocks to congratulate Mr Corbyn was the RMT - which only recently called off its strike action over the introduction of weekend all-night services on the Tube.
The RMT called his election "a massive shot in the arm for everyone fighting austerity, anti-union laws and for a return of our privatised services to public ownership".
There's been speculation that, even as early as this week's TUC conference in Brighton, the RMT will restore its affiliation to Labour, a link severed more than a decade ago.
One RMT source said there was no plan to re-establish the link yet, but that Mr Corbyn had made clear that workplace rights would be high on the political agenda.
The Fire Brigades' Union also disaffiliated more than 10 years ago in protest at Tony Blair's union reforms. It backed Mr Corbyn.
A shift in rhetorical tone is likely when the government's trade union reform bill is debated in parliament today.
Housing is the other main area of public policy where a pronounced hardening of approach is expected.
One of the most passionate sections of the new leader's victory speech on Saturday was where he vowed to end "social cleansing" in the capital and address what he sees as a chronic shortage of affordable homes.
New strictures on developers are expected along with tougher controls on the private rented sector and measures to tackle foreign ownership of property.
With Mr McDonnell at the helm of the shadow Treasury team, there will be speculation that local councils would be given more powers to build council homes again; restoring a right to borrow, in some form, which was removed by Margaret Thatcher.
An end to right-to-buy could well be advocated.
In terms of look and feel, there is also another striking shape to the shadow cabinet.
After years of dominance by northern and Scottish MPs, the capital may have found its voice.
As well as leader and shadow chancellor, London MPs now fill the shadow cabinet posts of health and chief secretary to the treasury. More could well follow.
- 14 September 2015
- 14 September 2015