U.K. Prime Minister Boris Johnson came out in support of top aide Dominic Cummings Sunday after a joint investigation by the Daily Mirror and The Guardian found Cummings had traveled 260 miles in April to visit his parents while exhibiting coronavirus symptoms.

The latest: "In traveling to find the right kind of child care, at a moment when both he and his wife were about to be incapacitated by coronavirus, and when he had no alternative, I think he followed the instincts of every father and every parent and I do not mark him down for that," Johnson said Sunday.

Polls suggest Americans consider the U.K. to be their country's closest ally, a distinction prized by a succession of British leaders and supported by decades of shared history and close cooperation.

Why it matters: President Trump has reveled in Brexit Britain’s rejection of multilateralism, in general, and the EU, in particular. But the U.K.'s voice will now count for less in Brussels and Berlin, and likely in Washington as a result.

Vice President Mike Pence told CNBC Friday that "we'll see" if the U.K.'s decision to allow Chinese telecom firm Huawei to build part of its 5G network will impact forthcoming trade talks between the U.S. and U.K.

Why it matters: Striking a trade deal with the U.S. is one of Prime Minister Boris Johnson's top priorities post-Brexit.

An image of the clock face of Big Ben was projected on 10 Downing Street, residence of British Prime Minister Boris Johnson, as Britain officially left the European Union at 11 p.m. London time.

Why it matters: "In its biggest shift since losing its global empire, [the U.K. turns] its back after 47 years on the post-World War Two project that sought to build the ruined nations of Europe into a global power," Reuters writes.

Britain's Brexit bill now only needs royal assent after lawmakers in the U.K.'s parliament ratified the legislation on Wednesday.

Why it matters: The ratification of the bill effectively ensures the U.K. will leave the European Union on Jan. 31.

The U.K.'s House of Commons voted 330-231 in favor of the European Union withdrawal agreement negotiated by Prime Minister Boris Johnson.

Why it matters: The bill must still be passed by the House of Lords, but the Commons' approval essentially ensures that Brexit will happen on Jan. 31. The passage of the bill after three years of deadlock is a result of the landslide victory Johnson's Conservative Party won in last month's snap election.

U.K. lawmakers approved Prime Minister Boris Johnson's Brexit deal on Friday with a 358-234 vote, showcasing the power of Johnson's new majority after last week's general election, per the BBC.

Why it matters: The vote puts the country on course for a Jan. 31 exit from the European Union. It'll also lock in a transition period through the end of 2020 — in which the U.K. will have left the EU but remain subject to many of its rules — in order for the government to flesh out new international trade deals and relationships.

Go deeper: Britain remade by Boris Johnson

Prime Minister Boris Johnson's landslide erased Britain's political map and upended its economy, The Atlantic's London-based Tom McTague writes on a stunning election with global echoes.

Why it matters: "[L]ess than four years ago, Johnson was still London’s mayor and undecided about whether to back Leave or Remain ... and Britain’s economy was among the most dynamic in Europe," McTague writes.

Millions of Britons are casting their votes today in what could be the most consequential election in living memory. One question now has less of a clear answer than ever: What will happen to Britain's terms of trade if it leaves the EU single market?

Driving the news: Polling suggests that Boris Johnson's Conservative Party will win about 43% of the votes. Under Britain's winner-takes-all voting system, that'll be enough to give him a modest overall majority in Parliament.

Senior British diplomat Alexandra Hall Hall has left the U.K. diplomatic service over Brexit, saying in a letter that she could no longer "peddle half-truths" for the leaders she does not "trust," CNN reports.

Why it matters: Her resignation comes a week before the UK general election, "at a moment of deep political sensitivity for UK Prime Minister Boris Johnson, who is seeking re-election on the promise that he can 'get Brexit done,'" per CNN. In her resignation letter, she wrote that she was unnerved to see the British civil service deliver half honest information on Brexit, and how that has undermined the credibility of British diplomats around the world.

Go deeper: Everything you need to know about Brexit