U.K. Brexit Secretary David Davis told cabinet colleagues to prepare for the possibility of Prime Minister Theresa May failing to reach a divorce deal with her European counterparts in the two years allowed by European Union rules.

Describing talks to quit the bloc as the “most important peacetime operation,” Davis called on government departments to “support a smooth exit from the EU” at the weekly cabinet meeting on Tuesday, May’s spokesman Greg Swift told reporters in London.

The Brexit secretary underlined “the need to prepare not just for a negotiated settlement but also for the unlikely scenario in which no mutually satisfactory agreement can be reached,” Swift said. “It’s important departments understand the challenges ahead.”

There was also a plea for optimism from May.

“She reiterated the need for an orderly process but stressed we must be optimistic, that our message is we’re not going to fail,” Swift said.

Separately, Foreign Secretary Boris Johnson told delegates at the British Chambers of Commerce annual conference that a deal can be done within the two-year window allowed by Article 50 of the Lisbon Treaty. May has pledged to trigger the process by the end of March.

David Fuller's view

For Brexit ministers, the challenges are immense but the opportunity to regain sovereign independence could not be more important for this country’s long-term development.  They have to deal with everything from querulous, angry Lords motivated by hubris - to nervous foreign corporate investors in search of reassurances - and disillusioned, bitter Eurocrats who cannot see or think beyond their own collective panic.

The UK team is doing well, led by our increasingly assured Prime Minister Theresa May, ably supported by the highly experienced wise heads of David Davis, the articulate Iain Duncan Smith and many others.

Assuming Article 50 is invoked this month, it is impossible to tell how long discussions will persist given Europe’s many elections.  Nevertheless, I maintain that the UK’s position is stronger than ever.