Scrivener finished a career high 32nd in the 2019 Race to Dubai Rankings Presented by Rolex courtesy of seven top ten finishes and looks to carry on where he left off at Hanbury Manor Marriott Hotel & Country Club.
The 31-year-old opened up with a birdie at the second but had to wait until the seventh to pick up his second shot, which sparked a hat-trick of gains to reach the turn at four under.
He carded another birdie at the 12th before picking up another stroke two holes later to move in contention.
A 20 foot birdie putt at the next saw the World Number 192 tie for the lead at seven under with Spaniard Adrián Otaegui, who then left the Australian on his own at the top when he bogeyed the 17th hole.
Scrivener was desperately unlucky not to extend his advantage as a lengthy birdie putt shaved the left edge of the hole at the 17th before a carbon copy effort at the last missed to the right, before his compatriot also carded an opening 64 in Hertfordshire.
Lee missed the cut during the first two legs of the UK Swing at the Betfred British Masters and Hero Open but made a superb run of birdies around the turn to move into contention.
Lee, who won the ISPS Handa Vic Open on home soil in February, picked up two shots and carded a bogey in his first four holes before his birdie trail began at the eighth and finished at the 12th to surge up to six under.
He parred his way to the 18th, where he hit a huge tee-shot before landing his approach from the rough to about 20 feet. He rolled in his eighth birdie of the round to join Scrivener at the top.
Jack Senior had earlier set the clubhouse target at six under after a sparkling front nine of 29 harboured thoughts of a possible first round 59 in Ware.
The 32-year-old was in the opening group and mounted his challenge from the off. He carded birdies at the first and second before extending his early advantage to three under with another gain at the par three fourth.
An eagle two on the par four seventh saw Senior jump to five under before successive birdies elevated him to seven under and turn in for 29.
A bogey at the 12th looked to have derailed his chance of becoming the second player to card 59 on the European Tour after Oli Fisher at the 2018 Portugal Masters, but gains on the 14th and 15th regained his momentum only to drop successive shots from the 16th hole to finish at six under.
Danish rising star Rasmus Højgaard, who has posted successive top ten finishes in the first two legs of the UK Swing, also registered 65 on the opening day after mixing nine birdies with three bogeys.
Otaegui was the brief leader after eight gains and bogeying the tenth but another dropped shot at the penultimate hole saw the Spaniard fall one shot behind Scrivener and Lee.
Former World Number One Lee Westwood and Thorbjørn Olesen, who won the 2018 Ryder Cup with Team Europe, led a group of five players at five under alongside Steven Brown, while Germany's Max Schmitt and Australian Maverick Antcliff were at that mark with two and five holes remaining respectively.