Robertson had reduced the deficit to one frame after Maguire stormed into a 3-0 lead, but the Scot quelled his brief resistance. Robertson held an 8-2 record over Maguire yet it was the Scot who built a 2-0 lead after decisive breaks of 40 and 39.
Robertson came back and his momentum continued after the interval, first breaking for 41 to ultimately secure the frame.
Yet the pendulum swung the other way once more when Maguire stopped the rot with an imperious 75, and his iron nerves were enough to see him over the line with a match-winning 38.
The real star of yesterday's show, though, was Ronnie O'Sullivan, who wowed the crowds at Alexandra Palace with a perfect display of snooker and admitted afterwards that Ricky Walden had been unfortunate to meet him in such a mood.
Walden started the better with a tidy opening-frame 39 but after breaking down would not make another pot as O'Sullivan rattled in 556 unanswered points to set a new snooker record, beating the previous best of 495 that was set by Ding Junhui in 2007.
Rewriting snooker history is nothing new to the Englishman but even he looked in shock after the brilliant win which was wrapped up in just 58 minutes and 31 seconds, giving television schedulers plenty to ponder - they had been due to broadcast for three-and-a-half further hours. "Ricky has had a good season and has won a couple of ranking events, he's a top player and I played well to beat him," said O'Sullivan, who joked he would now have the time to pick his children up from school.
The Englishman made breaks of 79, 88, 72, 134, 77 and 56 on his way to the win, with the final of those looking destined to be a maximum 147 until losing position after an attempt to split the pack.
"That's the first time I've ever felt helpless on a snooker table," said Walden, who in fairness did little wrong. "I scored about 35 points in the first frame then never saw another ball, really."