World Championship 2017: Mark Selby leads Fergal O'Brien 8-1 in opener
Defending champion Mark Selby dominated the opening session of his first-round match against Fergal O'Brien to open up an 8-1 lead at the World Championship.
The Irishman claimed the final frame of the session to avoid becoming only the second player to suffer a whitewash 10-0 defeat at the Crucible Theatre.
Leicester's Selby, who beat Ding Junhui in last year's final, looked completely at ease as he made breaks of 77, 53 and 56 to take the first eight frames.
The pair play to a finish at 19:00 BST.
O'Brien, 45, has taken only two frames in his five previous matches against Selby, stretching back to 2006.
He came through qualifying by beating David Gilbert in a final-frame decider - the longest frame in snooker history, timed at two hours, three minutes and 41 seconds.
But he struggled badly against the world number one, managing a high break of just 32, although he avoided the ignominy of joining Eddie Charlton - who lost 10-0 to John Parrott in 1992 - as the only players not to win a frame at the Sheffield venue.
In an all-Scottish tie, Anthony McGill trails qualifier Stephen Maguire 7-2.
Five-time ranking title winner Maguire has fallen to 24th in the world, but was in good scoring form, compiling breaks of 97, 66 and 60 to open up a sizeable advantage.