It was the best-known hole in golf, and certainly the quirkiest; now, it is also irrefutably one of the hardest.

The par-four 17th hole at St Andrews - The Road Hole - has been lengthened by 35 metres for the 150th British Open beginning this week, meaning it is now a dogleg of 450 metres. The tee has been moved back so far it is now outside the boundary of the Old Course, cut into the side of the St Andrews Trust practice range.

So the challenge that faces the world's best players this week is: a drive of 235 metres to clear the corner of a building which carries a sign for the Old Course Hotel. The best line here is debatable. From the forward tees, caddies used to advise pros and duffers alike to aim over the "O" in Course for the perfect line. Now, from the back tees, the pros have to be a bit more circumspect. "Anywhere over 'Old' is a good line," said England's Lee Westwood. "And no further right than L in 'Hotel'."

Anything further left than "Old" will end up in heavy rough, from where a par is difficult to salvage. If the drive does manage to find a sliver of fairway, a mid-to-long iron will be required to find the famous narrow green which runs perpendicular to the player and is protected at the front, of course, by the deep Road Bunker which has caused calamities to even the greatest players - Tommy Nakajima, David Duval, John Daly and Seve Ballestros among them. (That's American Tim Petrovic, pictured above, playing out sideways during practice overnight). A gravel path and then stone wall await the shot that is hit a few metres too long. Tom Watson, who came a gutser here in 1984, will attest to the difficulty of coming across them.

The changes have been, well, controversial is probably the best word. The likes of Ryder Cup captain Colin Montgomerie and new US Open champion Graeme McDowell have led the chorus of disapproval. Montgomerie said if the 495-yard hole had been suggested by a modern-day course designer he'd have been escorted from the premises, or worse.

"If you designed the hole now, you would be shot," said Montgomerie, runner-up to Tiger Woods here five years ago. "If you said now, 'I'm going to put a tee over an old railway on a practice ground and get you to hit over a disused course and over a hotel,' people would think you were off your head.

And the Chicago Tribune noted that some modern architects were mortified - ''as though someone had slipped eight pars of gangsta rap into God Save the Queen.''

But many argue: why shouldn't the penultimate hole in golf's most famous championship be a challenge? The 18th is just a pitch and putt par four from the widest fairway in golfdom, so it's only fair and reasonable that the world's best players have their mettle tested somewhere near the end of their rounds.

And on Sunday, the last four or five pairs in the field will be thinking about this monster well before they arrive on the tee, dry-mouthed and sweaty-palmed. For this is undoubtedly where the championship will be won and lost.

The changes were brought about by the R&A simply because the world's best players were only hitting eight- and nine-irons into the green for their second shots. Suddenly the Road Hole had become the Gentle Country Lane Hole. When Ballesteros beat Watson in 1984, the 17th had a 4.79 stroke average. That had dropped to 4.71 during Woods' 2000 romp and further to 4.63 five years ago, when Woods won again.

The only way to reverse the trend was to get the longer irons back into play on players' approach shots.

"This change will ensure that the hole plays as it was originally intended," R&A chief executive Peter Dawson said in making the announcement.

Two-time Open champion Padraig Harrington has defended the changes, and made a fair bit of sense in doing so.

He said the additional length had restored the fearsome nature the famous Road Hole had 20 to 30 years ago and said: "It's what you were used to seeing on the TV years ago and exactly what they need."

The Irishman, who won back-to-back Claret Jugs in 2007 and 2008, said: "It's an intimidating tee shot and a tight fairway but the way I look at it you always want to make sure that the guy who wins the Open is tested at some stage coming down the stretch.

"It's no problem with length and it's the same angle, it's just playing as a big hole - as it should be at the end of championship golf.

"There is no-one going to get through 16 holes without thinking about it for four days."

Harrington also felt criticism by players and golf course designers claiming the changes altered the history of the links was misguided.

"Everything evolves - you do realise they used to play this course from the greens to the tees, the reverse way round?" he said.

"I know 17 is very high profile but this is the modern game. I'm sure the old tee was probably not there 30 years ago.

"It has to change at some stage, that is part of golf. All courses, and this one in particular, has evolved over the course of time."

So settle back now, and watch the fun. When the wind whips up from the Firth of Forth, and Woods, Mickelson, Stricker and co are standing on that 17th tee, wondering whether to aim over "Old" or "Course" or "Hotel" and then, further along, trying to extricate themselves from the Road Bunker - which is deeper than anything they've ever come across on the US Tour - that could well be some of the best sporting entertainment of the year.