The home favourite saw off the challenge of Adrian Otaegui at Hanbury Manor Marriott Hotel & CC to win his fourth European Tour title and first since the 2015 Portugal Masters.
He started the day five shots clear but had that advantage cut to two as the Spaniard made a front-nine charge.
But Sullivan finished with a flourish on the back nine where he recorded four birdies to end on 27 under par - seven shots clear of Otaegui.
All of the 34-year-old's previous three victories came in 2015 and he was a relieved man to have his hands on silverware once again.
"It’s frustrating that I didn’t kick on from 2015 but it’s just one of those things," he said. "It feels like the weight of the world is lifted off my shoulders that I’m back in the winner’s circle. I’m just proud of myself to come back and get that win in the manner I did.
"It didn’t feel like a seven shot lead out there. I got on 12 and see that Adrian was two shots behind and breathing down my neck, and it was just nice that I could keep pressing on with the putter there – it just got hot."
Waiting for him by the 18th green was a laptop so he could speak with his family - and the tears started to flow.
Speaking about his emotions, Sullivan said: "I think it was just the people that have missed this win, my brother-in-law was only 24 and he was taken from us so it’s quite emotional for him not to witness it. It means quite a lot for me to do it for him today, and a good friend of mine has passed as well.
"So it means a lot to do that for them and it’s nice for my family, to win for my little boy who is only two years old, it’s just nice for him to see Daddy being successful, he hasn’t quite seen that yet. Also for me, I can’t remember too much about my emotions in the first three wins but I was fighting the tears back today down the last three holes.
"I’m proud of myself of what I’ve achieved this week and how I’ve gone about my business, I’m just really proud of myself."
Sullivan reached the turn with a three shot lead despite an eagle on the second as Otaegui recorded five birdies on the front nine.
The Englishman had given the chasing pack early hope when he found long rough and a bunker on the first hole, but he sunk a nerve-settling eight footer to save par.
His eagle on the second was his fourth of the week and moved him six shots clear of a congested chasing pack, with seven players tied for second at one point.
But a bogey on the fourth dropped Sullivan back to 22 under, while Otaegui followed up birdies on the first and second with back to back gains on the sixth and seventh to move within three.
Otaegui reached the turn in 32 and was just two shots behind as he birdied the par five ninth but Sullivan responded with his first birdie of the round at the same hole to restore his three shot lead.
Otaegui holed from just off the green on the 12th to again cut the lead to two shots but Sullivan once more responded with an eight footer to stay three ahead.
And Sullivan then holed a brilliant 20 foot putt on the par four 14th and followed it up with another birdie three on the next to move five shots ahead.
Otaegui faded and dropped a shot on the 17th when his 20 foot par putt came up just short before a par on the last.
That left Sullivan to head down the last with six shots in hand and he finished in style with another birdie.
Rasmus Højgaard finished third on 19 under after a flawless 64.
It was the impressive 19-year-old Dane's third successive top six finish on the UK Swing, following a second place finish at the Betfred British Masters hosted by Lee Westwood and last week's tied sixth at the Hero Open.
Fellow youngster Wilco Nienaber was fourth on 18 under.
The South African completed the front nine in five under, thanks to three birdies and an eagle on the second, and an impressive putt from the edge of the green on the par five 12th moved him to 19 under.
But the 20-year-old dropped a shot on the par five last to miss out on a first top three finish at his 13th European Tour event.
Steven Brown had started the day as the closest challenger to his 2011 Walker Cup team-mate Sullivan and ended the day fifth with a one under 70.