O’Sullivan came in as favourite after a devastating display against Ding Junhui in his semi-final on Saturday night, hammering the Chinese superstar 6-1 with four centuries along the way.
However, the Rocket was nowhere near that kind of form for much of the afternoon, especially early on as Trump took a 4-0 lead.
The Ace was playing well enough, with breaks of 74 and 69 in those four frames, but not spectacularly, with O’Sullivan struggling to get going.
After the interval the world number one did start to recover, taking the next two frames, with his first half-century (60) of the game in the sixth.
Trump guaranteed he would lead at the end of the session by taking the seventh and he looked in good shape to take a commanding lead but for some O’Sullivan brilliance in the last frame of the afternoon.
After both had chances early in the eighth, the Rocket produced an immense, improbable clearance of 63 to stay in touch at 5-3 behind.
Trump will be pleased with the advantage but not anywhere near as happy as he might be after taking a 4-0 lead and being pegged back. He had further chances to be even further ahead, but couldn’t capitalise.
‘In terms of standard it’s been disappointing, you have to say,’ Stephen Hendry said on ITV4. ‘In terms of what the players were playing before they gotto the final, especially Ronnie last night. But it’s been no less fascinating, to see who could get the other hand.
‘It took until the last very frame of the session for Ronnie to show some of that magic that he showed last night. At some times it was incredible how low the standard got.’
There will be no panic from O’Sullivan who was 5-3 down to Ali Carter after the first session of the Masters final just last week, then 6-3 behind shortly after the resumption.
The Rocket got stronger as the Captain weakened and eventually won the match 10-7 to claim an eighth Masters title.
It is game on ahead of the evening session starting at 7pm.
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