Lee secured the victory in style by winning the final frame on a re-spotted black after Robertson had come from 66-23 down to level the frame 66-66.
Lee took a tight opening frame that lasted 50 minutes 65-48 and then a break of 52 set him up for the second as Robertson failed to build on two decent scoring chances.
A great final long red saw him win the third after a 48 had put him in control before the final frame dramatics secured him the winners' cheque of £70,000.
Australia's Robertson saw his perfect record in televised finals broken as he lost for the first time in ten attempts. The 30-year-old Cambridge-based potter had to settle for the runner-up prize of £35,000.
It has completed a recent renaissance for Lee who reached the final of the World Open in China two weeks ago.
Lee dropped out of the world's top 16 in 2008 and appeared to be in freefall down the rankings. But he has found a second wind in his career and is now pushing for a place among the top eight
"I didn't let Neil get going, and in these short matches if you don't settle in the first couple of frames then you can lose 4-0," said Lee.
"A big thanks goes to Barry Hearn because he’s got all the lads buzzing about the game again. I knew I was good enough, I just couldn’t cope with playing six tournaments a year. There was so much pressure on every event and it was a horrible feeling.
"The game is in a great situation now and I just wish I was ten years younger. I’ve got the belief in myself back and I've beaten top players which is very satisfying. I appreciate it more now I’m older."
Robertson said: "The first frame set the tone, I had chances to win it but just couldn't take them. All the other frames were similar, I just lost the cue ball or missed something tricky when I was in the balls.
"Stephen's safety must be the best in the world at the moment and the way he's been playing recently it would have been a travesty if he hadn't won a tournament. Good on him because he looked dead and buried a few years ago but he has resurrected his career.
"It's disappointing to lose a final but it doesn't feel as bad as I thought it would. I've won nine out of ten finals which is still a good record."
The Grand Finals was the culmination of the PTC series which featured 12 other tournaments across the UK and Europe.