Nearly seven weeks after the weekend Night Tube was due to come into operation, the deadlock between unions and management over its introduction is as intractable as ever.

The start of the Rugby World Cup in September was meant to be an international showcase for the 24 hour city, but as the Australia v New Zealand final showdown looms, the initiative, which includes the Jubilee line, has been pushed back into the New Year.

In recent days, a new development has emerged. Unions (RMT, TSSA, Aslef and Unite) and management have tried to sidestep the impasse, and each other, in an attempt to open up negotiations in new ways.

TSSA has gone direct to the Mayor’s Office seeking face-to-face talks with Boris Johnson while London Underground is bypassing the unions and talking to staff, either directly or online.

The unions recognise that this dispute has a significant PR element and the apparent ease with which they inconvenienced Londoners prompted a move towards less bull-headed intransigence – not least because it was inviting a statutory clampdown on strikes by the Government .

So strikes have been cancelled , the benefits of the Night Tube have been acknowledged and a friendlier air adopted abroad.

TSSA general secretary Manuel Cortes said: “I have written to the mayor in good faith. I want him to use his considerable personal authority to get a grip of London Underground’s stalling tactics.

Canary Wharf Jubilee Line

“Our union accepts that a Night Tube service will benefit passengers, workers, tourists and the future economy of our great city. And our members will be proud to play a significant part in delivering the service that will transform London into a true 24/7 city.

“My personal, face-to-face offer to Boris stands. Meet me, and my fellow rail union leaders, face-to-face and let’s get the Night Tube back on track. Together we have the power – and on the part of our members at least – the willingness to make this happen.”

Mayor Boris Johnson has declined the invitation. His spokesman said: “The mayor has made clear negotiations are a matter for London Underground management. To do anything else risks undermining that process.

“Given the unions know that, it’s clear to the mayor that they are intent on needless headline grabbing rather than doing what they should be doing, and putting the deal to their members.”

London Underground is conducting “face-to-face” meetings of their own with staff and garnering online feedback. TSSA says this is “sneaking behind the backs of union leaders”.

Cast-iron guarantees

London Underground is convinced that its package – which involves more money and concessions over “quality of life” issues – would be agreeable to staff.

It believes unions are attempting to exploit the Night Tube – with its sizeable economic benefits to the capital – to leverage a gold standard package for members out of proportion to the scale of the changes. LU says the union demands would cost “hundreds of millions of pounds”.

LU managing director Nick Brown said : “We have made cast-iron guarantees that no one will work any more hours than they do today, drivers will have the same number of weekends off as now and, in future, staff will be able to choose whether they work Night Tube shifts at all.

"Everyone will retain their existing generous leave entitlement and we’ve hired an extra 500 people to help to deliver the new service. We’ve also offered an inflation protected pay deal and bonus.

“We and the mayor have repeatedly made clear that the introduction of the Night Tube would not be ‘at any cost’ to London’s fare and tax payers.

“They have not put the offer to our staff. So we will now seek the views of our staff directly on the pay offer, the implementation of the Night Tube and its operation.”

Sadiq Khan MP

Khan's conciliatory tone

London Underground believes that the fact the new deal has not been put to staff suggests unions are concerned their members are in less confrontational mood than the union bosses are prepared to concede – £200 per night bonus for a shift is appealing while Aslef has shown signs of wavering .

A defeat or concession would pave the way for more dramatic initiatives in future – such as driverless trains. This is why the unions are trying to put down a marker.

They are also looking to a more favourable climate if Labour’s Sadiq Khan takes City Hall in May. Famously the son of a bus driver, Mr Khan has suggested that his support for the unions would not be automatic although he has a more conciliatory approach.

Mr Khan said : “It’s not a question of one side or the other. All of us want Night Tubes running. My advice to TfL and the trade unions is don’t do this in the full glare of the media, get round the table and sort this out.”

Meanwhile, despite the tactics, the dispute remains heated. RMT general secretary Mick Cash said: “This crisis management of the Night Tube could have been avoided if LU hadn’t chosen to try and railroad through imposed rosters and had stuck to the agreed negotiating framework from the off.”

Where you will be able to travel on the Night Tube network

Service details

Running 24 hours, Fridays and Saturdays

Jubilee and Victoria lines : Trains running on average every 10 minutes across the entire lines.

Central line : Trains running approximately every 10 minutes between White City and Leytonstone and every 20 minutes between Ealing Broadway to White City and Leytonstone to Loughton/ Hainault. No service between North Acton and West Ruislip, Loughton and Epping and Woodford and Hainault

Northern line : Trains running on average every 8 minutes between Morden and Camden Town and every 15 minutes from Camden Town to High Barnet / Edgware. No service on the Mill Hill East and Bank branches

Piccadilly line : Trains running on average every 10 minutes between Cockfosters and Heathrow Terminal 5. No service on the Terminal 4 loop, or between Acton Town and Uxbridge

TfL also plans to expand the night time service to parts of the Metropolitan, Circle, District , and Hammersmith & City lines once modernisation programmes are complete.

Additionally, services could operate on parts of the London Overground in 2017 and the Docklands Light Railway by 2021.