Incredibly, the maximum was only the third of Williams' honour-filled career, which has spanned 30 years.
Aged 47 years and 270 days, the Welshman became the oldest ever to pot a 147 break, beating previous record holder John Higgins, who completed the feat at last year's British Open aged 46 years and 90 days.
The maximum on Friday was the 183rd official 147 in snooker and the seventh already this season.
Williams' other two 147s came at the Crucible in the 2005 World Championship and in the 2010 Rhein-Main Masters.
Williams was 3-0 down to Robertson when he pulled the effort out of the bag, having only scored 17 points in the previous three frames. He ultimately went on to lose the match 5-3.
Ronnie O'Sullivan boasts the most perfect breaks in history with 15, while Higgins has 12 and Stephen Hendry completed 11.
