London - Since Britons voted in 2016 to leave the European Union, Brexit has thrown the country's traditionally sedate politics into seemingly never-ending turmoil.

Here are a few big developments in the three-and-a-half-year saga, which has stirred growing frustration and dismay both at home and abroad.

- Two resignations -

Brexit has so far scuppered the premierships of two British leaders.

After six years in power, David Cameron resigned as prime minister in June 2016 the day after he lost the referendum on EU membership with 52 percent opting for Leave.

Just three years later, his successor Theresa May stood down after failing to win British lawmakers' approval for her Brexit plans.

Her replacement Boris Johnson is now battling to get the deal done.

- Three Brexit votes -

May tried to win parliament's approval for her European Union divorce deal on three separate occasions this year -- with each crunch vote billed as Brexit decision day.

But lawmakers rejected her agreement every time, throwing the process into disarray.

- Multiple delays -

Britain was originally scheduled to leave the EU on March 29, with May telling the House of Commons more than 100 times that this would be the date when the country departed the bloc.

However, after she lost the third so-called meaningful vote on her pact, the embattled leader was forced to ask for a Brexit extension.

Britain's departure was initially pushed back to April 12, before another delay request saw October 31 set as the new date.

But as that deadline loomed, May's successor Johnson was on Saturday forced -- by a law passed by opposition MPs -- to seek a third deadline extension this year.

EU leaders are currently considering that request.

- Two deals -

May spent around 18 months painstakingly negotiating her divorce deal, shuttling between London and European capitals to find common ground ahead of key EU summits.

Unable to overcome resistance in parliament, she was forced from office and Johnson took over in July, promising to rework several key elements.

Brexit re-negotiations with Brussels were eventually resurrected, with the new premier sending his envoys on still more rounds of shuttle diplomacy.

A beaming Johnson emerged from an EU leaders' summit in Brussels last week with his own, reworked Brexit deal, which he is now battling to persuade MPs to support.

But his early effort over the weekend and Monday stalled, and the process will resume Tuesday without any clear sign of when it might end.

- Two speaker interventions -

UK Parliament Speaker John Bercow, a colourful figure who has played a starring role in the ongoing drama, has made several crucial interventions of his own.

Most notably, on two occasions -- in March and again on Monday -- he refused to allow the government to submit its EU divorce deal for MPs to vote on.

Both times Bercow ruled it would breach the British parliament's opaque procedures for lawmakers to debate and decide on the same measure in the same parliamentary session.

- Two Queen's speeches -

Queen Elizabeth II has twice reopened parliament with a speech setting out her government's Brexit-driven agenda since the 2016 referendum.

In rolling out May's plans in June 2017, the monarch wore a purple-blue hat with yellow flowers -- which some saw as alluding to the EU and its symbolic blue flag adorned with yellow stars.