Harrington had begun his account with an eagle at the 337-yard third before dropping his only shot at the next hole.

Then the birdies began to flow as the Irishman reaped the benefits of a serious practice session with coach Bob Torrance, father of Ryder Cup captain Sam, on Wednesday.

He led by two strokes from Ryder Cup team-mate Phillip Price, who appeared to have maintained the form that helped him to a 3&2 victory over Phil Mickelson on Sunday.

On four under through nine holes over the Old Course at St Andrews, Price shared second spot with Eduardo Romero of Argentina, who was also playing Carnoustie, and Brian Davis of England, at Kingsbarns.

A five-man group on three under included Vijay Singh of Fiji, while Thomas Bjorn was in a large group on two under par.

Players and their amateur partners in this pro-am event were playing one round on each of the three venues over the first three days, with a cut coming ahead of the final round on the Old Course on Sunday.

Colin Montgomerie was one under through 12 holes at Carnoustie, as was Ernie Els, the Open champion who was second here last year.

Retief Goosen, battling to retain his Order of Merit title against the challenge of Els, was one over par, also at Carnoustie.

Paul McGinley, who holed the winning putt at The Belfry, was also one under, playing with Harrington with whom he won the World Cup in 1997.

Defending champion Paul Lawrie was level par having played the back nine at Kingsbarns.

The good scoring was no surprise as the event revelled in bright sunshine, in stark contrast to the bad weather which dogged the tournament last year. But a breeze blew up during the afternoon to make things a little tougher for the 168 pros and their amateur partners.