At the start of 2016, David Cameron was prime minister. His most likely successor was George Osborne. Whatever Cameron got in his renegotiation with Brussels, Britons were expected to vote to remain in the EU.
As the year ends, a long-serving home secretary-turned prime minister must keep her party together while negotiating the incredibly complex matter of how to leave the EU.
Try the HuffPost Politics Quiz of the Year to see how much you remember about what happened in between.