BEACONSFIELD, England (Reuters) - Over wet grilled sausages and red wine on a rainy British weekend, an evening garden gathering of ageing Conservative Party members seems an unlikely setting for subversion.

Vote Leave supporter and conservative, Roger Kendrick poses for a photograph at his home near Slough, Britain, August 31, 2018. REUTERS/Peter Nicholls

But that is what is happening here and in dozens of other gardens and village halls across the country, a phenomenon that could tip the scales in a parliamentary vote on how Britain leaves the European Union.

In the crowded kitchen in Beaconsfield -- an affluent commuter town outside London and Conservative stronghold -- there was angry talk about how Prime Minister Theresa May had sold short Leavers’ dreams of making a clean break with the EU and reclaiming Britain’s sovereignty.

“She has misled the country by giving the impression that we are leaving when we are not,” Roger Kendrick, an investor in small businesses, told Reuters at the meeting, a fundraiser for the Campaign for Conservative Democracy.

“She is lying to the country and thinks she can get away with it,” he said as he ate from a paper plate. “We are being conned.”

Kendrick’s opinion matters. The party’s 124,000 rank-and-file members, mainly volunteers but also paid local councillors, play a meaningful role under the UK’s political system, raising funds and rallying the local vote on election day.

If grassroots pressure can persuade just a handful of lawmakers to vote against May, they could kill the plan she is currently negotiating in Brussels.

With less than seven months to go until “exit day” on March 29, the future relationship between Britain’s $2.6 trillion economy and the world’s largest trading bloc is at stake.

The country remains divided on the issue - the result in the June 2016 referendum was 52 to 48 percent - and so is the Conservative Party, which called the vote.

Interviews in person and by phone with more than 25 party members across Britain show divisions between the grassroots in the counties and the leadership in London may go deeper than Brexit.

“We’ve been moving to this point for 20 years. Brexit is the issue that has brought it to a head,” said John Strafford, the host of the Beaconsfield barbecue.

“You end up with the parliamentary party 60 to 70 percent in favor of ‘Remain’, and the voluntary party 60 to 70 percent to ‘Leave’ - and that clash is actually going to be the end of the Tory Party.”

CHEQUERS PLAN

May’s “business-friendly” plan - named Chequers after the country house where it was agreed in July - prioritizes the smooth flow of goods and services with the EU over a clean break from Brussels’ rules and regulations.

The EU says further concessions are necessary; hopes for an agreement in October have been pushed back to November.

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May has pledged that whatever emerges will go to parliament for approval, probably before Christmas.

If she loses that vote, she will face the possibility of Britain leaving the EU without a deal, a prospect that would likely spark a crisis of confidence and probably cost her the premiership. It could even force an early election.

Her working majority of 13 members in the 650-seat parliament - 316 Conservative lawmakers, plus a Northern Irish party with 10 and minus MPs who don’t vote - only works if her lawmakers are united behind her. At the moment that’s a big if, as shown most recently in July when 12 pro-EU lawmakers voted against her on a piece of Brexit-related legislation.

The grassroots plays a key role here by holding lawmakers’ “feet to the fire”, said Tim Bale, professor of politics at Queen Mary University of London.

“So if they have committed to a hard Brexit it makes it difficult for them to renege on that commitment.”

Some, like Chris Green, a Conservative MP from Bolton West, have already been turned.

Green resigned from a junior role in the transport department in July because of his opposition to the Chequers deal, and plans to vote against the proposal if it comes to parliament.

Lying just a few miles north west of Manchester, his constituency has traditionally been viewed as bellwether of national political trends and voted 56 percent for Brexit.

Green, who won his seat by just 936 votes at the last election in 2017, is concerned that his supporters will desert him to join the eurosceptic UK Independence Party (UKIP).

“The views on the proposed deal have been almost universally negative and there is an element on despair creeping in,” he said. “We have a clear instruction from the British people and any deviation from that will cause problems and divisions.”

A regular party meeting in August near the south coast city of Southampton to discuss health and social policy was swamped by members wanting to talk about Chequers and Brexit.

According to two of those present, the meeting, which usually attracts a dozen diehard members to feed policy ideas to the leadership, drew more than 50 people. Only two supported the Chequers plan versus leaving without a deal, according to minutes of the meeting.

Relaying the findings to party headquarters, the meeting’s chair, Allan Glass, wrote in a letter seen by Reuters: “Implicit in our observations is that the Chequers proposals are wholly misconceived and undesirable, and the government should drop them as soon as parliament reconvenes.”

Bob Perry, chairman of the Conservative association in Hornchurch and Upminster, east of London, said around 10 of his group’s 160 to 170 members had resigned or declined to renew their membership since the Chequers agreement was unveiled.

“She (May) needs to listen to the grassroots because we are at the end of the day the foot soldiers, the people who pound the streets, knock the doors, deliver the leaflets, and if you can’t get them behind you then you are going to have a problem.”

In Beaconsfield, Strafford has started a petition to stop the sitting MP, Dominic Grieve, from running as the party’s candidate at the next election scheduled for 2022, mainly because Grieve led several pro-EU rebellions in parliament.

Grieve declined to comment on the petition.

Kendrick says he can’t remember a time in the 30 years he has been a member of the Conservatives when there have been such deep divisions among members and such a disconnect between the leadership and rank and file.

BEYOND BREXIT

While polling shows the Conservatives neck and neck with the opposition Labour Party nationally, a Sky Data poll in August said that among the party’s voters, 59 percent are unhappy with May’s performance in Brexit negotiations.

Potential successors to May are waiting in the wings, including former foreign minister Boris Johnson, who resigned days after the Chequers deal was announced and is actively campaigning against it.

For many at the grassroots, Johnson’s leading role in the 2016 Brexit campaign and his mix of humor and common man’s touch makes him an ideal replacement.

John Thorne, a local councillor in the southwestern county of Somerset who wants May to be removed, supports Johnson.

“People love Boris. He is the sort of guy you imagine sitting down in the pub and having a pint with,” Thorne said.

“I have confidence in him to deliver Brexit and he speaks the language of ordinary people.”

The overwhelming majority of party members interviewed saw little future for May even if she manages to scrape by as their leader beyond March.

Britain’s role in Europe helped sink the country’s last three Conservative leaders: David Cameron, John Major and Margaret Thatcher.

Now some wax nostalgic for Thatcher, including Glass, who attended the gathering in Beaconsfield.

“I just wish she could be a bit more like Maggie, and go over there and give them a good handbagging,” Glass said, holding court under a dripping umbrella as Strafford’s sausages smoked in the rain.