Home Secretary Sajid Javid has resigned as Britain’s finance minister and government in a showdown with Boris Johnson and Prime Minister Theresa May over the future of Britain’s approach to Brexit.

The resignation, which came in the early hours of Wednesday morning, was timed for maximum political impact. The most senior minister in the government, Mrs. May was still out of the country in Saudi Arabia, and has only released a short, carefully-worded statement condemning Mr. Javid’s decision to quit. “While I disagree with the decision he has taken, I wish him well,” she said in the statement.

Mr. Javid stood up to the hard-right elements of the Conservative Party, which have argued that Britain should leave the EU immediately after the two-year negotiations on Brexit end and return to the World Trade Organization terms.

But in his resignation letter, Mr. Javid suggested the UK should approach the negotiations with a “pragmatic and realistic approach.”

“Whilst I continue to strongly believe that we should make a success of Brexit, I have concluded that the practical, legal and political realities of leaving the EU mean we cannot do so without fundamentally changing our approach to government and public policy,” he wrote.

The departure of Mr. Javid – who is seen as an attempt to rally a centrist faction within the Conservatives who supported Remain in the June referendum on whether to leave the EU – followed a gruelling day in parliament, where a revolt by ministers on Brexit caused May to look and sound nervous.

“I continue to believe that the best outcome for Britain is for us to succeed in securing a good Brexit deal for Britain,” he said. “However, I am of the view that it is best for the government to have a full, all-party focus on delivering Brexit in an orderly way in order to protect the economic and national interest.”

The departure will also reignite calls for Conservative Party conference next month to be suspended.

And the conservative Party’s national executive is set to discuss whether or not the conference, scheduled for the end of March, should take place at all. Those calling for it to be delayed or cancelled cite the prospect of a chaotic departure from the EU on March 29, the date of a scheduled Brexit summit, which could force the government to ask for an extension of the Article 50 process.

In his resignation letter, Mr. Javid accepted that such an extension was likely, but insisted: “We cannot risk meeting these deadlines for leaving without a deal.”

“If we fail to secure a good deal for Britain,” he continued, “then I will do everything I can to prevent the backstop being used to tie the UK to the EU.”

The government is still preparing for a “no deal” Brexit on March 29, however, under which the U.K. would fall out of the customs union.

Mr. Javid is the second member of May’s cabinet to quit since he was appointed as home secretary in July.

Ministers leaving the government are exempt from ministerial resignations if they prefer to continue in the party. And their exits affect the stability of the government because it could strengthen opposition parties.

Just weeks before the general election in June, Mrs. May called a snap general election for June 8 in order to strengthen her hand in Brexit negotiations. But her Conservative Party government lost its majority in the election and she was forced to govern with a minority government after failing to gain a working majority in parliament.