Beginning with an eagle at the 12th hole, Webster played his final seven holes at 5 under par to claim his second career European Tour win and first since 2005.
A bogey at the 18th hole kept him from a spotless round, but the final mistake only served to trim his winning margin. It was followed by a fist pump, then the waterworks as the Englishman tried to hide his tears by covering his face with his hand.
Webster finished at 25-under 263, two shots better than Robert Karlsson.
He had a lot to play for.
'I lost my mom in the early part of the season and it really knocked me back. I didn't think I'd even get my card, really,' said Webster, who now has a two-year exemption. 'It was quite tough. I had a good result at Loch Lomond (tie for eighth place) and seemed to turn the corner a bit and I started being a bit more positive.
'I thought, 'I've got to win this thing,' and I just can't believe I did it.'
Karlsson, playing alongside Webster, had his second consecutive 7-under 65 to finish alone in second place at 23-under 265. It was the best finish this season for the seven-time European Tour winner.
Daniel Vancsik held the 36- and 54-hole leads for the second straight week, but again finished in third place.
There was nothing on Vancsik's scorecard like the quintuple-bogey he made last Sunday at the Madrid Open, but he only managed a 1-under 71 in the final round to end six shots off the lead at 19-under 269.
Vancsik was joined at 269 by Lee Westwood (68), Fredrik Andersson Hed (66) and Peter Hanson (68).
Webster and Karlsson, playing in the second-to-last tee time, both got off to hot starts. Webster made three birdies on the first five holes and four overall on the front nine, while Karlsson birdied five of his first nine. Webster's birdie at No. 9 gave him a share of the lead with Vancsik.
'I got off to a great start, but so did Robert. We both played well and pushed each other along,' Webster said.
Webster moved two shots ahead of both Karlsson and Vancsik when he set up an eagle at the par-5 12th with a stunning approach shot. It was his only eagle of the tournament.
'I just hit a great 5-iron in, and it really focused me,' he said.
The eagle sparked a run of good golf, with Webster making a birdie at the next hole then back-to-back birdies at the 16th and 17th. His 2-foot birdie putt at the 17th secured a three-shot lead and allowed Webster to make the stroll down the 18th fairway as a soon-to-be champion.
'I shoot a 72 today and I finish 10th, or something. You shoot a good last round and you move up and win, which is an amazing feeling,' he said.
'It's so hard out there. I was thinking about [my mom] all the way around. It's just so hard to keep my mind on my golf. But I know she was watching me today.'