Scotland’s David Law produced a “pretty unbelievable” second round to lie a shot off the halfway lead in the Porsche European Open in Hamburg.

Law tamed a 7,455-yard course known as the Green Monster as he fired an eagle and eight birdies in a seven-under-par 66, a nine-shot improvement on his opening 75.

That drew high praise from the man at the top of the leaderboard, Germany’s Max Kieffer adding a 71 to his opening 69 to reach six under par, a shot ahead of Law, England’s Jordan Smith and Northern Ireland’s Tom McKibbin.

“First of all, seven under is pretty unbelievable,” Kieffer said when told of Law’s score. “That’s a crazy round of golf.

“It’s playing quite long, even though it’s a bit shorter this year than the last few years. There’s lots of water, the greens are quite undulated.

“If you hit a loose shot here and there, usually on every hole there’s a bit of trouble. It’s a very tough course.”

Law could easily have gone even lower than 66 after starting on the back nine and following six birdies in his first eight holes with an eagle on the par-five 18th to be out in 30.

A bogey on the second halted his momentum and although he birdied the fourth and seventh, Law bogeyed his last two holes of the day.

“I went out there just trying to play golf and make birdies and score as low as I can,” the 32-year-old said. “The brakes came on a bit on the back nine, but it’s a difficult course, it’s tough.

“The goal is to keep doing what we were doing. I tried hard on the back nine to keep in the present and make birdies like we were, but it didn’t happen. Barring the last two holes we played really nice on that second nine.”

Arguably the shot of the day belonged to Law’s compatriot Ewen Ferguson, who putted out of a bunker on the 14th and holed from 25 feet for birdie.

“The sand is very firm and compact,” Ferguson said after a 72 left him three off the lead.

“It was a narrow green and I thought if I didn’t get the strike right (with a sand wedge) it could have trickled into the water or I had to go left of the pin.

“I thought I’d putt it and it rolled nicely didn’t it? I’ve never had that before. You just have to go for it and see what happens. Just smash it out and get lucky.”