The Road Bunker and road behind the green are famous golfing landmarks
St Andrews' famous and notoriously difficult Road Hole has increased in length for the 150th anniversary of the Open Championship in 2010.
A new tee has stretched the 17th hole by 40 yards, five more than announced last year to 495, to prevent shorter irons being used to avoid hazards.
The change is the only major alteration from five years ago, when Tiger Woods won his second Open title.
The course now measures 7,305 yards compared to 7,279 in 2005.
The decision to alter the length of the Road Hole for the first time in more than 100 years was taken in conjunction with golf's ruling body, the R&A.
And it has been claimed that they were following the advice of three-time Open champion Henry Cotton in advance of the 1964 Open.
"I would make a tee just beyond the railway line on the other course," he had said. "It would restore this drive to its former value."
Cotton had been talking about the Eden Course, which is now the practice range, where the new tee has been built, increasing the length of the Road Hole to 490 yards.
This change will ensure that the hole plays as it was originally intended
R&A chief executive Peter Dawson
However, the course card lists the hole as 495 yards.
The R&A says the change will place "an increased premium" on an accurate drive of sufficient length over the sheds, encouraging players to take a driver from the tee.
Widening of the fairway on the left hand side will "ensure that the tee shot remains fair".
The R&A says that this will re-establish the difficulty of the second shot, making it more difficult to hold the approach on the putting surface and increasing the threat posed by both the road behind the green and the Road Bunker.
R&A chief executive Peter Dawson said: "The 17th was played at the same yardage in 1900 as it was in 2005 and this fuelled our belief that the formidable challenge of this iconic hole should be returned for The Open Championship.
"Over the years, we have seen the threat from the road behind the green, and to a lesser extent the Road Bunker, diminished as players have been hitting shorter irons for their approach shots, allowing them to avoid these hazards more easily.
"This change will ensure that the hole plays as it was originally intended."
Five new tees had been introduced for the 2005 Open at St Andrews, lengthening the course by 164 yards.