Speaking yesterday, Johnson said a preferred route for the scheme had emerged following a recent consultation.
This would see the construction of a new line running from Wimbledon via a new station at the Kings Road in Chelsea and on to existing stations including Tottenham Court Road, Angel and Dalston Junction. This ‘core’ line would have terminals at both Tottenham Hale and New Southgate.
Additional regional routes using existing rail lines could potentially run on from Wimbledon, Tottenham Hale and New Southgate to serve places including Twickenham, Epson and Cheshunt.
In a statement the London mayor’s office said Crossrail 2 would support the delivery of up to 200,000 new homes across London by introducing new capacity "and allowing new residential suburbs and districts to be created".
The statement said the Department for Transport will consult on proposed changes to the safeguarding, updating the previously safeguarded Chelsea – Hackney line, which dates back to 1991.
"The consultation will engage with the relevant local planning authorities and will also inform occupiers whose land and property is within 200 metres of land that may be needed in the future. Subject to the outcome of the consultation process, the secretary of state will issue a safeguarding direction for Crossrail 2 in 2015", it said.
A spokesman for the mayor said the safeguarding direction would cover the entire core route.
The mayor’s office said the the next steps for the project would be a consultation on a single preferred route option and station/worksite locations from September 2015.
"More detailed design will then be needed and an application for powers to build could take place in 2017 with the railway being operational by 2030", it said.
The statement said Johnson was "confident" that London "could in the right circumstances contribute well over half the cost of Crossrail 2, reducing the demand on the UK taxpayer as a whole". It added that Johnson and mayoral agency Transport for London "believe the wider UK economic and transport benefits ... support the case for a government contribution to the cost".