Don't make promises you can't keep.

Matthew Goodwin, a professor of political science in the United Kingdom, tweeted last month that he didn't believe the Labour Party under Jeremy Corbyn would poll above 38 percent in the U.K. general election. If they did, he said, he would "happily eat [his] new Brexit book."

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Well, Labour got 40.3 percent on June 9. And now Goodwin is on live TV eating not just his words, but his book.

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The book, as Goodwin surely wants you to know, is Brexit: Why Britain Voted to Leave the European Union. It's available for £15.99 on Amazon if you'd like a snack too.