Update: as expected, moments ago Boris Johnson joined the Brexit vote saying "I've decided after a huge amount of heartache I will be advocating the UK to leave the European Union" because he wants a better deal for the people of the country.
More coverage from SkyNews below:
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Yesterday, when we summarized the statements by UK politicians regarding the June 23 EU referendum, we said the one most important opinion has yet to come: that of London mayor Boris Johnson's whose "opinion may sway the vote one way or another in four months. As the Telegraph reproted that "David Cameron is mounting a last-ditch effort to woo Boris Johnson to back his campaign to stay in the European Union, by drawing up plans for a new constitutional settlement that puts the sovereignty of British institutions beyond doubt."
As the Telegraph added, "sources close to Johnson said he remained “genuinely torn” and that he would “chew over” what the prime minister has to say when Cameron appears on the BBC’s Andrew Marr Show on Sunday, before issuing some form of statement this evening. He will then spell out the reasons for his decision in his column for the Daily Telegraph on Monday."
It appears that Cameron's effort to "woo" Johnson has failed because moments ago BBC reported that "Boris Johnson is to campaign to leave the EU in the UK's referendum, BBC understands."
The Guardian has more:
Boris Johnson is to transform the terms of the EU referendum by announcing that he is to throw his weight behind the campaign to take Britain out of the EU, according to the BBC.
In the biggest boost to the Leave campaign so far, the London mayor is to announce that after much soul-searching he now believes the time has come for Britain to sever its EU membership.
The news was broken by the BBC’s political editor Laura Kuenssberg who tweeted: “Boris WILL campaign to leave the EU -Huge boost for Out, big blow for number ten altho expected - more soon. Official announcement tonight.”
The report was being seen at Westminster as authoritative because Johnson recorded a broadcast interview in which he was due to explain his thinking.
Last night we said that "if Johnson refuses to back Cameron, the Friday afternoon spike in the GBP may be very promptly undone." NOw that this appears to be the case, keep a close eye on cable once it opens in a few hours in Sunday's illiquid trade - it could get volatile.