If you were to ask every caddie if they have ever "given a mystery" and they were to give an honest answer, it would be a unanimous yes; at least one. The "Agatha Christie" (mystery) if given often enough, is a sackable offence. So what is it?

One of the caddie's basic duties is to tell his player how far they have to where they want to hit the ball. We provide this information in Europe with the invaluable assistance of Graeme Heinrich's yardage book.

This is a small handmade course chart with the needs of the professional golfer highlighted. Basically the first 200 yards of par fours and fives are ignored. Detail in the landing area for drives and around the green is given priority.

Paint is sprayed on the fairways in the landing area for drives and from there distance are given to the front of the green. A pin sheet is provided each day indicating the daily flag positions. So, with the aid of this yardage book, the caddie and golfer should know how far they have to go.

They should know. However, calculations have to be made. Although it does not involve complicated mathematical computations, caddies and enumerations adds up to "mysteries" or mistakes. Numbers given by adding on paces instead of deducting them, reciting a number for the tenth hole reading from the ninth page etc. For whatever reason, they happen.

Worming your way out of the "mystery" situation depends on your player's disposition and, of course, the severity of the mistake. Mac O'Grady, so the story goes, once fired a caddie while his ball was still in mid air.

Back when Nick Faldo was a more threatening contender, his caddie gave him a number which was 25 yards too long. It was getting dark, they were on the last hole and there had been a rain delay. Any more excuses? As Faldo was extending his right arm after impact into a perfect Leadbetter follow through, his caddie's sphincter twitched with the realisation of his mistake.

The ball disappeared into a murky twilight. A loud clang was heard out of the evening silence. Faldo asked if that was the sound of his ball hitting the pin, indicating his level of expectation from such a perfect swing. His caddie decided that a quick admission of guilt and an attempt at humour was the best way out of his predicament. He replied promptly: "No, Nick. That was the sound of your ball hitting the grandstand behind the green, directly on line with the pin. That yardage was a bit out. It was a great shot, though."

Luckily for the cad, Faldo had a great short game and, believe it or not, a sense of humour.

With the use of modern measuring equipment the occurrence of numerical mistakes in the yardage book has been reduced. Within the time-span of about a decade measuring has evolved from simple pacing (wide variation), to a distance wheel (consistent) and today many caddies use lasers (precision) to conquer the logistical problems of charting modern golf courses.

The Robert Trent Joneses do not build caddie-friendly golf courses, either for walking or measuring. They have created a greater need for measuring with lasers. The modern course tends to look more like an assault course than a golf course. To provide accurate yardages with a yardage wheel is virtually impossible as there tend to be ponds or lakes on every other hole.

Once we hear a new venue is a Trent Jones design, we know we are in for a tough week. Simply walking a new course compared to an old one you quickly realise that there is no flow or logical progression to the new ones, especially when you have 15 kilos of metal on your back.

You are frequently backtracking over pretty bridges or walkways in order to reach tees or greens. When playing on traditional links or older courses a common sensation is of rolling on to the next hole, not trekking in search of it. So, with the evolution of courses, it has become necessary to use more advanced measuring techniques.

In the late '70s and early '80s, when caddies use to make their own yardage books in Europe, mainly by pacing the course, there were obviously some discrepancies. It's difficult to give an accurate yardage when the numbers written in your book are wrong. I can only assume the players relied more on feel back then.

A caddie known as "Silly Billy" got as far as July of one season with a blank yardage book. He carried what looked like a yardage book, but when his player snatched it out of his hand during a round to see what was in it, he discovered 18 blank pages. This had been going on for months. Obviously, instinct was the main tool of his decision making.

Later, the same Billy decided to become a bookmaker on tour. That must also have been an empty book as he ran into financial difficulties shortly after setting up shop. All bets were cancelled.

You may wonder why the player doesn't carry his own yardage book to limit the "mysterious" number risk. Well, the truth is that an increasing number of players do. If either caddie or player miscalculates then one of them should spot the mistake. Traditionally the player does work off instinct and will frequently have mentally selected a club before the caddie gives him a number, using the number only as a confirmation.

In windy conditions, for example, yardages do no have the same significance in the decision making process. Most players will recognise if a "mystery" of any proportion has been given. The subtle two or three yard variations for a good professional with a wedge in his hand can be costly and difficult to recognise. The chances are the caddie will get away with smaller errors. Depending on who he's working for, of course.

While playing a four-ball match in the Ryder Cup, one European player inquired if a yardage he was given by his partner's caddie was from the back of a sprinkler or the front. A sprinkler is only about 20 centimetres in diameter. Guess which player from continental Europe could require such precision? Is modern golf that precise? As a caddie, if you work for a player who requires such accuracy then you must provide it. Whether it's relevant is another matter.