this time the finishing score line was reversed as Selby lost the deciding frame 5–6. He retained his China Open championship in April, defeating Barry Hawkins 11–3 in the final. This was Selby's third China Open title in four years. Later that month, his two-year reign as World Champion ended in the first round of the World Championship, where he fell to Joe Perry 4–10, unable to recover from a 2–7 deficit in the first session. In winning the match, Perry became the first player to beat Selby at the World Championship since Anthony McGill had defeated him in the second round in 2015. Despite this disappointment, Selby still finished the season as world number one. 2018–19 season At the World Open in August, Selby lost 4–5 to world number 53 Noppon Saengkham in the last 16, losing the deciding frame by just three points. He won his 15th ranking title at the China Championship in September, defeating John Higgins 10–9 in a very close-fought final. He reached the semi-finals of the Northern Ireland Open in November, losing 5–6 to Ronnie O'Sullivan on the final black. He faced disappointments in other tournaments, including an unexpected 3–6 loss to amateur James Cahill in the first round of the UK Championship. At the 2019 Masters, he lost 2–6 to Judd Trump in a "nervy" quarter-final, despite making a 110 break in the seventh frame of the match. Selby lost the top ranking position to O'Sullivan on 24 March 2019, having been world number one since February 2015. O'Sullivan reclaimed the top spot by winning his 36th ranking title at the Tour Championship; Selby had himself been eliminated in the first round by Neil Robertson in a final-frame decider, after squandering a four-frame lead. He had an opportunity to regain the top spot at the China Open less than two weeks later, but lost 3–6 to Craig Steadman in the qualifying round which had been held over from the original qualification stage in February. At the World Championship, Selby beat Zhao Xintong 10–7 in the first round before being defeated 10–13 by Gary Wilson in the second round. As a result of this mediocre performance, he ended the season as world number six, having also been outranked by John Higgins, Neil Robertson, Mark Williams and Judd Trump. 2019–20 season In the 2019–20 season, Selby reached the semi-finals of the International Championship, losing 4–9