In the 2003–04 season, O'Sullivan reached three ranking-event finals. He reached the final of the British Open, but lost 6–9 against Stephen Hendry. He won the Welsh Open by defeating Steve Davis 9–8. He reached the final of the Masters, but lost 9–10 against Paul Hunter, despite having led 6–1 and then 9–7. In 2004, O'Sullivan's father telephoned six-time World Champion Ray Reardon, and asked if he could give O'Sullivan some advice. With Reardon's help O'Sullivan recovered his form, and won the 2004 World Championship. He defeated Hendry 17–4 in the semi–finals, the most one-sided defeat ever in a World Championship semi–final. He then defeated Graeme Dott 18–8 in the final, despite losing the first five frames. O'Sullivan blamed his poor start on "mind games" by Dott's coach Derek Hill, who visited O'Sullivan's dressing room just before the match. O'Sullivan was ranked number one for the next two seasons. In late 2020, in a Eurosport special The Joy of Six, O'Sullivan told Colin Murray the interviewer that his poor start had been to do with being unsettled by seeing his past coach and friend Derek Hill in his opponent's corner. He had in fact been very angry at him felt it was a betrayal of sorts but his coach Ray Reardon was able to keep him focused enough to turn his game around and win.