The World at One
BBC Radio 4

Former Labour leader Ed Miliband, a Remain campaigner, says there is a need for candour from the government about difficult trade-offs, but that the Remain side of the argument must also engage to get a progressive deal.

Differing opinion across the UK on Brexit are the subject of sharp debate between the SNP's Angus Robertson and Theresa May.

Theresa May has invoked it with a letter, but what is it, can it be reversed and what happens next?

Image source, Reuters

It's been a busy few hours so here's a recap of what's been going on and what it all means for the process of Brexit. 

• Theresa May's long-awaited letter notifying the EU of the UK's plan to leave has been hand-delivered in Brussels
• In the six page letter, the PM said the UK bore no ill-will to the EU and wanted a "deep and special partnership" with it in future.
• She insisted that the UK wanted talks on the terms of exit and a future trade relationship - which are scheduled to take eighteen months - to be conducted at the same time, not separately

• In response, European Council president Donald Tusk said the EU "missed the UK already" and regretted its decision to leave
• He said his main focus would be on protecting the interests of the other 27 states in the forthcoming talks, expected to see the UK leave in 2019
• Draft guidelines signalling the EU's approach to the upcoming negotiations will be published on Friday
• Tory MPs welcomed the triggering of Article 50 while opposition parties criticised what it said were attempts to link trade to security co-operation.

Image source, AFP

Image source, PA

Alex Forsyth
Political correspondent

The key points of Theresa May's letter dissected

3)The tone of the letter

• What does the letter say?  "We should engage with each other constructively and respectfully, in a spirit of sincere cooperation."
• What's the significance? At the start of a negotiation, tone is key. In this letter Theresa May deliberately avoids an aggressive stance. She set out how the UK is the EU's closest friend and neighbour and why a continuing relationship between the two is essential to both. Rather than make threats or set out red lines, Mrs May strikes a positive and cooperative tone - more so than in the speech she gave about Brexit at the start of the year. Given the time pressure and sheer complexity of this negotiation and just what's at stake for all involved, the prime minister seems to be saying to her EU counterparts - let's work on this together. It might be welcomed by those on the other side of these talks - but some hard-line Brexiteers may want to ensure there's still a tough approach behind the softer tone.

House of Commons
Parliament

Image source, HoC

The statement concludes and Speaker John Bercow thanks the 113 MPs who questioned the prime minister.

He also thanks the prime minister "who has been with us for the last three hours 21 minutes". 

House of Commons
Parliament

What practical concessions has the UK government made to devolved governments? asks SNP MP Patricia Gibson.

Or, she wonders, is it a case of "lemmings unite"?

The prime minister replies that there are many areas where she has common ground with the Scottish government including the need to protect workers' rights.

House of Commons
Parliament

Image source, HoC

Labour's Chris Matheson asks if new executive agencies will be needed to be replace EU agencies such as Euratom or medicines control.

He asks how many new agencies will be needed, how much they will cost and whether the government can the government staff them.

Theresa May replies that she is aiming for a "comprehensive free trade agreement".

The World at One
BBC Radio 4

Former Conservative Party Leader and Leave campaigner Iain Duncan Smith told the World at One that there had been a "shift" in the rhetoric from other European countries over Brexit and that it was not in the interests of Europe to negotiate a bad deal, which would leave Europe not having access to vital goods and services in the UK.

House of Commons
Parliament

Image source, HoC

SDLP MP Mark Durkan says the Belfast Agreement rests, in part, on "a cross-island" cooperation in key areas.

He asks how the government can maintain the agreement whilst arguing that there can be "no differential arrangement" for Northern Ireland.

Theresa May says she is "very conscious" of the practical issues that arise from Brexit.

She adds that she is working "very closely" with the Irish government.

Theresa May is taking the UK in a "reckless and damaging" direction over Brexit, Labour leader Jeremy Corbyn says.

BBC News Channel

Nigel Farage said he would be celebrating the triggering of Article 50 and the former UKIP leader has been true to his word.

He has just given an interview to the BBC's Vicki Young outside his favourite Westminster pub.

In reflective mood, Mr Farage says he does not believe the UK should simply stalk out of the EU without trying to reach an agreement, pointing out that the UK had an enormously strong negotiating hand given their respective trade positions.

But his magnanimity did not extend to the EU, which he said did not work and should be dismantled to allow sovereign nations to run their own affairs.

He says Theresa May's wish for a strong EU was illogical and it was wrong for the UK to say other states should continue to be "run by Mr Juncker" when it was breaking free of that arrangement itself. 

A Swansea glass recycling firm is worried overseas trade might be more difficult after Brexit.

Leaving the EU - what are the key issues for Wales?

A marked change in tone from the PM in her letter to the EU still leaves Brexit battles to be fought.

BBC Radio 5 live

Image source, @JGBS

All across the UK today, BBC Radio 5 live is finding out what people have to say about Brexit. 

Leave voter Jimmy, from the Aberdeenshire port of Peterhead, entered the fishing industry in 1976 - the very early days of the EU. He says it's a huge day for the UK fishing fleet. "Surely as an island nation and a fish-rich sea, we should have the better of the deal, rather than our European cousins? [...] I've seen the industry contract and get smaller and communities decimated, by the might of the European Union".

Image source, @markhutchings1

Louise is a shop owner in Strabane, County Tyrone - which sits right on the border with Ireland. Her costume jewellery and handbag business has already been affected by the value of the pound, as she buys a lot of her stock from international suppliers. Louise also gets a lot of customers coming over the border from Ireland, so she is wondering if movement between the countries might change in the future.  Despite this, she is trying not to worry about it: "I'll just keep trading the way I am and hopefully it'll all work out in the end".

Now it has triggered Article 50, does the UK definitely have to leave the EU?

The SNP's leader Nicola Sturgeon says unanswered questions around the impact of Brexit mean the triggering of Article 50 is a "leap in the dark".

The letter triggering Brexit talks plays down fears of Westminster power grab, says BBC Wales's David Cornock.