Following David Cameron's resignation, it was up to our new Prime Minister, Theresa May, to negotiate a deal with the EU in an attempt to deliver Brexit. She gave notice of our intention to leave in March 2017, but feared getting any deal past Parliament. Because of this, she called an early General Election.
May's attempt to increase her majority backfired. Now she would need the consent of opposition MPs to pass her deal. However, it was Brexiteers within the Conservative Party who proved to be her downfall. They rejected her deal again and again, and even called for a vote of no confidence in their leader.
Ultimately, Theresa May was forced to resign. Her attempts to find a middle-way which kept Brexiteers and Remainers happy, were doomed to failure. She left office in July 2019, the second UK Prime minister to be brought down by Brexit.