His 68 included a Hunting Course-record 30 on the front side.
A 33-year-old from England, Tunnicliff is 18 holes from his first European Tour title. It would be a special one, considering his mother died of cancer a month ago. This is his first tournament since.
"It was a hard time for me because she had seemed to recover and was given the all clear," he said. "But then it came back with a vengeance and that was that. But she told me to go out and win, so I am trying my best to do that."
Tunnicliff's 30 on the front nine was a shot better than the course record set by Ross Drummondd in 1996 and matched by Australian Richard Green last year.
After making six birdies on the front side, Tunnicliff had a pair of bogeys on a birdie-free back.
"It was a tough, windy day, so it was inevitable I would do that coming home," said Tunnicliff, who ranks 62nd on the Challenge Tour and 280th on the Order of Merit. "I didn't want to make mistakes."
Gilford came home in 32 to earn a share of the lead with his playing partner and Struver. The Englishman had four birdies on a bogey-free back nine.
"It was nice to play with Miles because he started very well and I hit a couple of loose shots early on, but I kind of got dragged along," said Gilford, who lost a playoff to Carl Pettersson in the Algarve Open two months ago.
Struver began the day with a one-stroke lead but struggled to a 40 on the opening nine. The 34-year-old German came home in 34.
"I am pleased with the way I came back," said Struver, a three-time winner on the European Tour. "It could have got worse for me after my front nine, but I saw the guys up front weren't making that big a move."
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