LONDON (Reuters) - Fearing Britain could drop out of the European Union without a deal by design or default, one British lawmaker on Saturday masterminded a plan to deny Prime Minister Boris Johnson his day of Brexit glory.

Independent MP Oliver Letwin speaks at the House of Commons as parliament discusses Brexit, sitting on a Saturday for the first time since the 1982 Falklands War, in London, Britain, October 19, 2019, in this screen grab taken from video. Parliament TV via REUTERS

Oliver Letwin, 63, is a former cabinet minister with a reputation as an unofficial fixer, using his affable manner and procedural knowledge to head off awkward disagreements in parliament. Brexit has given him notoriety as a rebel with a cause: to stop a no-deal Brexit.

The first Saturday sitting of parliament for 37 years was supposed to frame the approval of Johnson’s EU divorce deal, succeeding where his predecessor Theresa May had spectacularly failed, by winning a vote to accept the exit agreement.

But instead Letwin, expelled by Johnson from the Conservative Party, snared the prime minister in a legislative booby-trap.

In a move showing the level of mistrust on both sides of the Brexit divide, Letwin passed a 26-word amendment that, he says, removes any chance of a no-deal Brexit by deferring a decision on Johnson’s deal.

Letwin scored 322 votes, Johnson only 306.

The result turned Johnson’s Brexit finale on its head, leaving the prime minister exposed to a humiliating obligation to ask the EU for a delay until the end of January 2020.

“I’m not daunted or dismayed by this particular result,” the prime minister said afterwards. “I will not negotiate a delay with the EU, and neither does the law compel me to do so.”

One pro-Brexit Conservative vented his frustration at the architect of the defeat: “Letwin is a pariah.”

After Johnson had left his seat in the debating chamber, his team then blindsided parliament by announcing plans to schedule a vote on his Brexit deal on Monday - putting Letwin on alert for another possible clash.

“The decision of the house today when it passed the amendment ... was specifically that the house was withholding approval unless and until the legislative stages of implementation had occurred,” Letwin said in response.

“And this very clearly flies in the face of that.”

‘NATION AT RISK’

Letwin was one of 21 Conservatives expelled from the party in September for not supporting Johnson’s pledge to leave the EU on Oct. 31 with or without a deal, and he has focused his parliamentary acumen on preventing a no-deal Brexit.

Letwin criticized Johnson’s bid to present lawmakers with a “deal or no deal” choice.

“I, despite my support for the prime minister’s deal, do not believe that it is responsible to put the nation at risk by making that threat,” he told parliament during Saturday’s three-hour debate.

His proposal sought to close a loophole whereby hardline Brexit supporters could have voted for the deal on Saturday but then blocked the legislation needed to implement it, leaving Britain on course for a disorderly exit at the end of the month.

Letwin’s amendment said parliamentary approval for the deal, required in order to ratify it, should be withheld until the government has passed the legislation needed to implement the exit agreement.

The proposal defeated Johnson because it united a diverse section of lawmakers who oppose Brexit altogether or want a second referendum, with those who support leaving the EU but only if that is with an exit deal.

While the motivation of the amendment was fear of Brexit betrayal, the proposal stoked a similar mistrust among Brexit supporters - who saw in it a plot to sink Britain’s departure in a legislative quagmire.

“It’s a wrecking amendment, hiding behind the transparent veneer of opposing a no-deal outcome in the hope of giving the Remain Parliament an opportunity to force through a second referendum,” Conservative Brexit supporter Andrew Bridgen said.