Philip Hammond, the Chancellor, has offered private reassurances to one of Wall Street's most powerful investment banks that he is pushing for a lengthy transition deal to help the City prepare for Brexit.
Sky News has learnt that Mr Hammond addressed a meeting of Goldman Sachs (NYSE: GS-PB - news) ' board in London three weeks ago to help soothe concerns about a possible 'cliff-edge' exit from the European Union (EU).
A source close to the Treasury said that the meeting between the Chancellor and Goldman's board took place on 29 June, but was not publicly disclosed by Mr Hammond's department.
While meetings between ministers and individual companies are not unusual, it is relatively rare for members of the Government to address entire boards of directors.
Insiders said that Mr Hammond had not given Goldman's directors any special assurances that were not apparent from his public attempts to reassure the business community that the Government is aware of its concerns.
The focus on a Brexit transition period after March 2019 has acquired greater urgency in recent weeks as a growing number of big City employers have begun to announce their plans for coping with Brexit.
This week alone, Citi has confirmed plans to establish a new trading hub in Frankfurt, which will involve the relocation or abolition of about 150 London-based jobs, while Deutsche Bank (IOB: 0H7D.IL - news) and Morgan Stanley (Xetra: 885836 - news) have also affirmed their commitment to the German financial centre.
On Friday, Bank of America Merrill Lynch said it would use its existing operation in Dublin to become its post-Brexit EU hub.
Other announcements from big City employers are expected after the summer break.
Mr Hammond has been leading a battle within the Cabinet to secure an extended transition period of around two years.
The Chancellor has appeared to gain traction in his quest in recent days, with Liam Fox, the International Trade Secretary, telling Sky News' political editor, Faisal Islam, that he now accepted such a period as "common sense".
His meeting with the Goldman board, which includes businessmen such as Lakshmi Mittal, the steel tycoon, underlines the distance between him and Theresa May, the Prime Minister, in terms of engagement with the private sector.
Having dismantled David Cameron's business advisory body after taking office, it took until this week for Mrs May to hold a formal roundtable summit with private sector bosses to discuss Brexit and its implications.
Mr Hammond has been much more willing to meet big City employers, although his discussions with Goldman directors may nevertheless renew controversy over perceptions of unduly close access to ministers for large companies.
"As you would expect, the Chancellor regularly meets with businesses to hear their views, most recently participating in the PM's business advisory group and hosting a roundtable with asset managers," a Treasury spokeswoman told Sky News.
Mr Hammond has also met a number of other bank bosses, including JP Morgan's Jamie Dimon, in the last few months, while on Thursday he held talks with senior fund managers and Chris Cummings, chief executive of the influential Investment Association.
Goldman employs around 6500 people in the UK, most of whom are based in the City, but has also been drawing up plans to relocate some of their jobs to other EU centres.
Lloyd Blankfein, the bank's chairman and chief executive, has also forecast that New York will be a beneficiary of Brexit.
Earlier this year, he said that the City would "stall" as a consequence of the UK's EU departure, while Richard Gnodde, the head of Goldman's international operations, told the BBC on Friday that he wanted early clarity on the details of a transition period.
Goldman declined to comment on its meeting with Mr Hammond.