Louis Oosthuizen made a solid start to his round as he attempted to protect his four shot advantage at The Open Championship.
The 27 year old South African, attempting to land a first Major at St Andrews, started the day clear of Paul Casey on 15 under par.
Two regulation pars were enough to extend his overnight lead from four to five shots, playing partner Casey missing a five foot birdie chance on the first and then dropping a shot on the second after coming up short of the green.
It looked like being a two-horse race between the leading pair, with none of the other contenders able to make an early impression.
Henrik Stenson misjudged his approach to the first so badly he came up short of the burn, but while playing partner Martin Kaymer overcompensated and ended up three-putting from long range, Stenson chipped on and saved par.
Spain's Alvaro Quiros had set the clubhouse target on five under after carding a 67.
Oosthuizen dragged his second shot to the par five fifth into deep rough, but hacked out onto the green and two-putted for another safe par.
Casey could only three putt from long range for his par too and it was not until Kaymer holed from 12 feet on the sixth that anyone in the last four groups had made a birdie.
That took Kaymer into outright third on eight under, with Oosthuizen still five clear of Casey on 15 and ten under respectively.
Casey finally made a move in the right direction with a birdie from four feet on the sixth to get back to four behind, while Kaymer missed from a similar distance on the seventh but holed from ten feet on the next.
Meanwhile, England's Luke Donald finished birdie-eagle to join Quiros and Jeff Overton as clubhouse leaders on five under, but World Number Two Phil Mickelson came home in 41 to card a closing 75.
