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How timely is this helpful explainer? Very! Tactical voting and election pacts are featuring prominently in this year's campaign. But how do each of them work?

Find out more in our feature.

BBC Politics Live
BBC2's lunchtime political programme

On a day when the SNP are championing their climate change policies, some, including the Greens, point to their support for continuing oil and gas extraction.

SNP candidate Kirsty Blackman tells Politics Live it is about a "managed transition", but adds that the Scottish government has not received enough support from Westminster.

"What we need is the UK government to step up to the plate, to agree with the ambitions that Scotland is putting forward about our climate change targets," she adds.

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Things are getting a bit trickier for Jo Swinson over the issue of whether or not to stand in certain seats... see the row over Canterbury and - when we finish beavering away on it - a new story coming on this very issue.

The Liberal Democrat leader has been forced to defend her decision to field candidates against Labour MPs who oppose Brexit - potentially splitting the Remain vote.

Jo Swinson says her party can't form an alliance with Labour because Jeremy Corbyn is "trying to deliver Brexit" which goes against what her party is trying to achieve.

A reminder: Mr Corbyn isn't firmly against Brexit, instead planning to reach his own Brexit deal with the EU and then offer it up against Remain in another referendum.

Speaking on a campaigning visit in Crouch End, north London, Ms Swinson said the Lib Dems were "proud" to have achieved an agreement with the Green Party and Plaid Cymru - more on that here.

However, she went on: “Labour have been absent from all that - they are not a party of Remain, they are trying to deliver Brexit and that is contrary to what we are trying to achieve in this election which is to stop Brexit and give people the change to vote to stop Brexit."

BBC Politics Live
BBC2's lunchtime political programme

Speaking of Jeremy Corbyn and Scotland, he's been talking this morning about the possibility of a second independence referendum, indyref2, in the event of a Labour government in Westminster.

The BBC's Nick Eardley says according to a Labour source, the party is “absolutely” ruling one out next year - which is when Nicola Stugeon wants it. The SNP has made it a condition of propping up any Labour minority government.

But the SNP's Aberdeen North candidate Kirsty Blackman tells Politics Live "the call is irresistible" if the SNP win big in December.

"If we have the people of Scotland standing up and saying we support the SNP who are standing on a platform, saying that Scotland's future should be in Scotland hands, I think the UK prime minister should have to justify themselves if they want to say no."

The former Scottish Labour leader says Labour "will have to look to other parties for support" to form a government if they don't recognise that.

BBC News Channel

On his visit to Glasgow, Jeremy Corbyn has sought to present this election in Scotland as a two-way choice between Labour and Boris Johnson's Tories.

But SNP leader Nicola Sturgeon hits back, saying Labour are not competitive in many Scottish consituencies.

"The key thing in this election is the only party that can beat the Tories in Scotland is the SNP," she tells the BBC.

"We are the main challenger in every Tory-held seat. A vote for Labour risks letting in the Tories."

Ms Sturgeon says that on many issues Mr Corbyn is "weak" and that SNP MPs would stand up to the Tories as well as keeping a potential Labour government in Westminster "on the right track".

BBC Politics Live
BBC2's lunchtime political programme

One of our writers here is listening to BBC2's Politics Live where they're discussing the row over the Lib Dem candidate for Canterbury. Tim Walker stood down to allow Labour a clear run, but the Lib Dems are planning to replace him - to some consternation.

Financial Times journalist Miranda Green tells Politics Live, "It's more than a little local difficulty, it gets to the heart to what this election is about, whether Brexit is the only thing you should care about?

"Or is providing a choice to voters, who may not fancy Jeremy Corbyn as prime minister, should they have another choice?"

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Earlier, Labour's shadow health secretary Jonathan Ashworth played down his party's policy to introduce a four-day - or 32 hour - working week.

When asked on BBC Breakfast whether the NHS was part of the plan, Mr Ashworth said "no".

"The idea that the NHS is going to go to a four-day week on 13 December if Labour get in is just for the birds - it’s nonsense."

John McDonnell says more on the idea and confirms the NHS is included, just not straight away.

"It’s a 32 hour week implemented over a 10-year period, it will apply to everybody. What Jon was talking about this morning was how you apply it over that 10-year period."

He said the Tories had given the impression it would be introduced if, and as soon as, Labour was elected on 12 December.

But, he said, it is a policy that has to planned and negotiated over time.

"It’s not an overnight thing - it’s a realistic ambition," Mr McDonnell said.

After their event on the NHS, shadow chancellor John McDonnell and shadow health secretary John Ashworth took questions.

The former said he thought Nigel Farage's decision for the Brexit Party to ditch plans to take on the Tories in more than 300 seats will help Labour.

He said "it absolutely clarifies now that we have a Trump alliance" - with Nigel Farage and Boris Johnson following US President Donald Trump’s orders.

"When our people go to vote I want them to be thinking of the risk of Farage and Johnson doing that deal with Trump to sell off our NHS to US corporations."

This has been an oft-repeated attack line by Labour during this election campaign - so we have looked into whether the NHS could be up for sale.

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SNP leader Nicola Sturgeon is on the campaign trail at a project funded by the Scottish Government's Climate Challenge fund in Edinburgh.

She is calling on Westminster to "get its act together" and match Scotland's progress on climate change with a Green Energy Deal - and says SNP MPs will demand "radical action".

The SNP wants the UK to draw up a plan for funding wave and tide energy projects and to pay to scrap polluting diesel cars.

"Westminster has wasted years obsessing over nuclear power and a complete lack of vision and ambition over the energy technologies of the future," Ms Sturgeon says.

Scotland has committed to reducing its carbon emissions to net-zero by 2045 - five years earlier than the rest of the UK.

But Scottish Green Party co-leader Patrick Harvie says the SNP cannot claim the moral high ground while it is committed to extracting every "last drop of oil from the North Sea".

The prime minister got a frosty reception from some locals, amid wider criticism of his handling of the crisis. He insisted he was in no way underestimating the scale of the situation.

Sarah Smith
Scotland Editor

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After a dramatic fall in support, the party has been squeezed out of the biggest debate in Scotland. Read all about it.

One of the charges against Jeremy Corbyn from former Labour minister Tom Harris earlier today was that he would help break up the UK by offering a new referendum on Scottish independence.

Now Mr Corbyn has addressed that head on, telling reporters he would not agree to an independence referendum in the first term of a Labour government - meaning not for five years.

But BBC political correspondent Nick Eardley says that Labour aides have briefed that the position could change if the SNP wins a majority in the Scottish Parliament elections in 2021.

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A Lib Dem candidate is threatening to stand down if his party does not apologise to one of his colleagues.

On Tuesday, fellow party member Tim Walker announced he would not run in Canterbury against Labour's Rosie Duffield, as he was worried about splitting the Remain vote and letting the Tories take the seat.

Ms Duffield won the constituency from the Tories at the 2017 general election with a majority of only 187 votes.

But despite his decision, the Lib Dems say they will select another candidate and still run in the Kent constituency.

Guy Kiddey, who is due to stand for the party in High Peak, says he will step aside unless the party stops disciplinary proceedings against Mr Walker and "apologises unreservedly" to him.

But he doubts the party will say sorry, and says he plans to resign his membership and vote Labour if they don't.

In a statement on Twitter, external, Mr Kiddey says: "How many times do voters have to say they are sick of this style of politics before anyone listens?

"In all the campaigning I have done so far, the thing people want more than anything else is the tirades and aggression to stop."

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If you're just joining us or you need a refresher at the end of the morning, here are the main developments so far today:

• On a visit to flood-hit areas, Boris Johnson insisted he didn't underestimate the impact of the situation, as he faced heckles from some onlookers for what they saw as his slow response
• Meanwhile, Jeremy Corbyn has travelled to Scotland where he says the election is a straight choice between the Tories and Labour. He was also jeered by a protester who suggested he symapthises with terrorists. Remember, the SNP hold by far the most seats in Scotland
• Former Tory minister David Gauke urged people to vote Lib Dem to avoid a "disastrous" Brexit outcome
• On the Labour side, former minister Tom Harris urged people to vote Tory, saying Mr Corbyn was a threat to national security
• Labour has promised up to £6bn more a year for the NHS to cut waiting times and boost mental health services
• The Lib Dems have pledged £500m a year for youth services to tackle knife crime - Jo Swinson is the latest politician to swing some punches in a boxing gym on the campaign trail
• And Baroness Warsi has said the Conservatives have failed to deal with "vile" Islamophobia in the party, as 25 sitting and former councillors are accused of racist posts - minister Michael Gove insists they will investigate the issue

Image source, AFP/Getty Images

The Green Party has been making its latest campaign pledge, saying it will appoint a "carbon chancellor" if voted into power.

The job of the new official will be to allocate the £100bn per year they have pledged for tackling the "climate emergency".

Co-leader Jonathan Bartley says the chancellor will lead a new department and issue an annual carbon budget.

Read more about the party's plans here.

All in all, the big borrowing the Greens want would add up to a trillion pounds over 10 years - here, BBC Reality Check looks more closely at how they say they'd find that sort of money.

John McDonnell finishes his speech at the Royal Society of Medicine in central London by saying he hopes people see Labour’s true colours - “a commitment to care, underpinned by a serious plan which shows we are ready to govern”.

Shadow health secretary Jonathan Ashworth has now taken to the stage to give more detail about Labour’s NHS plan, but he also starts by criticising Tory cuts to the health service.

He says he is anticipating NHS performance figures on Thursday “confirming our very worst fears that we are heading into a winter of absolute misery for patients”.

"Our NHS is crying out for a financial rescue plan and real change - that is what Labour is outlining today," he says.

There is a lot of to-ing and fro-ing about who's standing where as we approach the deadline for submitting nominations on Thursday.

Yesterday, the estranged wife of a Conservative MP who sent sexual messages to two consituents took his place as the election candidate.

Andrew Griffiths said he was standing down from front-line politics and was backing his wife, Kate, who won the nomination.

But Mrs Griffiths, the Tories' new candidate, tells BBC Radio Derby's political reporter that she does not want or accept her husband's support.

BBC Radio 5 Live

Nigel Farage stood down hundreds of Brexit Party candidates the other day to give the Tories a boost.

He called it "a unilateral Leave pact", and speaking on the Emma Barnett Show, Conservative candidate for North West Cambridgeshire Shailesh Vara said he wasn't aware of any deals.

"We’ve made it absolutely clear that we would stand firm and stand in every single election," Mr Vara said.

Brexiteer Tory Bernard Jenkin told the same programme he had personally had "informal conversations" with figures from the Brexit Party aimed at persuading candidates to stand down, he emphasised that as he wasn't a minister or part of the Conservative leadership, these weren't official talks.

"We’ve not been rescued by Nigel Farage, it’s just Nigel Farage has rather wisely agreed not to sabotage the thing that he’s been working for, which is Brexit," he said.

From Jeremy Corbyn back to his shadow chancellor. John McDonnell's speech has moved on to the NHS, and he begins by attacking the Conservative Party's record.

He says “we’ve always known you can’t trust the Tories on the NHS”, adding that their record is one of "running down" the service.

He’s says it’s been “nearly a decade of savage cuts”, and he highlights the "failure to recruit nurses" as contributing to leaving the NHS in “crisis”.

The Labour Party “is the party of the NHS”, he says, and will offer a package "to end the Tory NHS crisis".

Here's our story on what Labour is offering. The Conservatives say the plan isn't deliverable.

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Jeremy Corbyn is visiting Scotland as part of his campaign trail.

Speaking at a rally in Glasgow after donning a tartan scarf, he says Labour will fight the election "on the principles of social justice, on the principles of economic development and on the principles of environmental sustainability".

He says the party's plans will lead to thousands of jobs in the green sector, will protect the NHS and will put a final Brexit deal to a referendum.

Mr Corbyn says: "When the choice comes on 12 Dec, it is very simple.

"Are we going to have a Tory government with the injustice and poverty it brings... or are we going to have a Labour government in the great traditions of our party and our movement to provide... health and hope to the next generation and care for the older generation?

"I believe the people of this country deserve better than Boris Johnson and his government, and the country would be better off with a Labour government."

He concluded: "More Labour MPs for Scotland will mean a louder voice for Scotland."

In 2017, the SNP won 35 seats in Scotland, the Tories 13, Labour seven and the Lib Dems four.