'Shrek is OK but do not call me Lodewicus'

Louis Oosthuizen answers to most things except Lodewicus Theodorus, which he was named, after his grandfather. "Not even my family can call me that," he said. "I won't talk to them if they call me that. That's a passport name. I've always been Louis, right from the beginning."

But more recently he has become "Shrek", after the animated ogre. The relaxed 27-year-old South African has a dazzling smile, which ironically he displayed liberally when explaining the nickname. "It's the gap in my teeth," he said. "My friends say I look like Shrek – some of my friends. You can't choose your friends, so what can I say?"

He used to have a Shrek headcover but his caddie threw it out of the bag because he thought it was bad luck. Oosthuizen did not want to offend the caddie so went along with it. How laid-back is Oosthuizen? When he picked up a new sports car from the sponsors at the BMW PGA Championship and drove it home to Manchester, only to find it was too wide for the garage doors, he simply bought new doors.

As the world No 54, his name is hardly unknown, just unpronounceable. A number of low rounds and high finishes on the European Tour have meant the cognoscenti have had to get used to mangling the Oosthuizen name – it's Wuhst-hy-zen, apparently.

But when you are leading the Open Championship and have equalled the St Andrews halfway record of 12 under par, you might expect to be introduced correctly in the media centre. But the "Well done, Peter!" greeting he was not expecting, since he has rarely been confused with the giant Englishman Peter Oosterhuis, the former Ryder Cup player. Graciously, Oosthuizen just laughed it off.

"It's probably the position anyone wants to be in, playing a major on the weekend," he said, sticking to the real matter at hand. "It's what we work to achieve and I'm just happy with the two rounds I've put together." He was even happier as his 67, impressive in the tricky morning conditions, became even more valuable as Rory McIlroy and the other later starters headed into the afternoon gales.

Though Oosthuizen has shown a particular liking for the desert swing on the European Tour in the Middle East, where conditions are far removed from those buffeting St Andrews this week, he grew up playing at Mossel Bay club, on the Garden Route, where you can see the sea from every hole and where it can also get pretty windy. Eight years ago he knocked it round there in 57, with two eagles and 11 birdies, so he is not afraid of the wind or the mental challenge of "going low", as the professionals say.

For three years before turning professional Oosthuizen was in the Els Foundation, based at Fancourt. "It was unbelievable what he did for me," he said. "He helped with expenses and travelling round the country but mainly he was just a great mentor. Probably without him, I wouldn't be here now."

Up to the age of 10 Oosthuizen played a lot of tennis – it runs in the family – but as soon as he picked up a golf club he was hooked. He has won five times on the Sunshine Tour at home but his first win in Europe did not come until the Andalucian Open in March, when not even the naturist beach next door distracted him.

Returning to Manchester, his base over here, he had to leave the trophy at Malaga airport because Monarch Airlines deemed it a "dangerous object" and refused to accept it as hand baggage. What Oosthuizen did bring home was a bundle of confidence.

"I've been playing well all year but the win got my confidence going," he said. "I had been a bit frustrated on the golf course for a few years because I knew I could win tournaments, I'd done it at home, but it never happened in Europe. But I set my head to have fun, to make sure I enjoy myself. You know, life is not just about golf."

With more than 24 hours to kill before teeing off in the third round, Oosthuizen went back to his rented house with his wife, Nel-Mare, and their seven-month-old daughter, Jana. "She will definitely occupy me for the rest of the day," he said. Oosthuizen is not the first golfer to find his best form now that he is called "Daddy".