Mark Selby made the first maximum break in a World Snooker Championship final as he reeled off the final three frames of an exhilarating opening day to trail Belgium's Luca Brecel 9-8 overnight at the Crucible.Forty years after Cliff Thorburn compiled the first 147 in the tournament, four-time champion Selby polished off the 15th to add his name to the list of history-makers at the famous venue.Selby's maximum earned him a share of the £40,000 tournament highest break prize with Kyren Wilson, who also made a 147 in his first-round win over Ryan Day.His achievement capped an absorbing first two sessions in which Brecel threatened to pot his way into a significant lead only for the 39-year-old to show all of his renowned tenacity to drag himself back into contention ahead of Monday's conclusion.Twice previously in finals, against Ronnie O'Sullivan and John Higgins, Selby has trailed heavily only to roar back and clinch victory and he is now a heavy favourite to finish the job against Brecel, who before this year had not won a match in five visits to the Crucible.Having carved a reputation as a comeback king after his wins over O'Sullivan and Si Jiahui, the Belgian found himself in uncharted territory as a front-runner after blazing a trail with some epic long pots to take the first session 6-2.Breaks of 77 and 90 helped him punish Selby, who uncharacteristically missed an easy brown and two blacks off their spots and was seemingly suffering after his early-hours semi-final win over Mark Allen the previous night.In a thrilling start to the evening session, Selby summoned a 134 total clearance only for Brecel to respond with a high-octane 99, including a series of trick-shots on the colours, to immediately restore his