Miguel Angel Jimenez carded a 67 to finish alone in third place at 8-under-par 130. Jean-Francois Lucquin followed at 7-under-par 131 after a round of 66.
Tadini, who has made only five of 15 cuts this season on the European Tour, played the back nine first and tallied a birdie on the 10th hole of the Roman Road Course at Celtic Manor Resort. He hit his tee shot to 12 feet for a birdie at the par-3 15th and kept on rolling with a birdie at the par-5 16th.
The 31-year-old Italian hit his second shot to 7 feet at the par-4 first and drained the putt for another birdie. Tadini then birdied the par-3 second and converted an 8-foot putt for a birdie at the par-5 third to make it three in a row.
At the par-4 fifth, Tadini played his second shot inside 10 feet and rolled in the birdie try to hold the 36-hole lead for the first time in his European Tour career.
'Beautiful putting today,' said Tadini, who won on the Challenge Tour in 2004. 'It's a nice course.'
Lynn was part of a six-way tie for first after the opening round and he started his second day well with back-to-back birdies from the second. He stumbled to a bogey at the par-4 fourth, but came back with a birdie at the very next hole.
The Englishman added a birdie at the par-4 seventh and a birdie at the par-4 10th lifted him within one of Tadini at 10 under par.
Lynn missed a 7-foot putt for a bogey at the par-3 15th, but he ran home a 5-footer for a birdie at the 16th to get back to minus-10. Lynn found trouble with a bogey at the 17th, however, and parred his way in to finish two shots back.
'Conditions were fairly tricky out there,' said Lynn, who posted a 66. 'Playing a golf course for the first time you're always learning as you go along.'
Jimenez collected two birdies and a bogey over his first nine holes, but he found trouble early on the inward half with a bogey at the 10th. The Spaniard made a move with back-to-back birdies starting at the 14th, but he dropped a shot at the 16th. Jimenez countered with a birdie at the following hole to finish alone in third place.
Welshman Ian Woosnam shares fifth place with Christian Cevaer, Richard Finch, James Heath, Benoit Teilleria and Francois Delamontagne at 6-under-par 132.
The 36-hole cut came in at 1-over-par 139 with 80 players qualifying for the weekend including defending champion Simon Khan, who finished on the number. Colin Montgomerie, who recently gained entrance into the U.S. Open, was among the notables who missed out along with Thomas Bjorn and Nick Faldo.