The three most common of these are Chief Financial Officer (CFO), Chief Operations Officer (COO) and Chief Technical Officer (CTO, often referred to as the CIO or Chief Information Officer), but the new economy is often throwing up new positions of senior executives with increasingly outlandish titles such as Chief Evangelist. Saints be praised.

The routes into these elevated positions are different, but each brings with it the opportunity of rising to the level of CEO. Defining the "number two" in a large company is often tricky, with the CTO least likely of the C Suite to fill that particular role, but each member of the club will play an active part, not only in the management of the company, but also in planning its future direction.

Still, because of the importance of finance to corporate strategy, it is often the CFO who is ostensibly second in command, with the greatest opportunity to advance to CEO level.

"It is usually a toss-up between the CFO and the COO as to which is the second most senior position, but in the majority of cases, it is the CFO who is the de facto number two, " said Mark O'Donnell, director, human capital at Deloitte. "In fact, CFO tends to be a more likely breeding ground before executives take up the position of CEO."

In terms of the differences between the roles, the COO tends to be the person who gets his or her hands dirty (or at least as dirty as senior executives' hands can get).

The CEO is the strategist, reviewing past performance and looking to the future, while the COO is the person who is charged with project management, and implementing the company's strategy. Hence, the COO is closer to a truer definition of a managing director.

"COOs come from a variety of backgrounds and, in the new economy, there tends to be a very strong project management element to the role, " said O'Donnell. "Some COOs will have been brought through the business, and will have a deep understanding of the company, while others may come from a consultancy background.

Essentially, there are two types of Chief Operations Officer . . . there is the top tier, MBA-type former-consultant COO, and there will be those who have been in the business a long time."

The CFO's job is mainly in the financial sphere, although that will frequently go a long way to dictating strategy. The majority of CFOs come from an accountancy background, although there are some highprofile cases where this is not the case (for example, Patrick Coveney of Greencore). But practically all will have a sort of "blue chip" background, with most possessing "big four" (or "five" or "six", depending on when they qualified) accounting experience. They will usually have then worked their way up the corporate ladder, through positions such as divisional accountant and group financial accountant, before leaving the nuts and bolts of accountancy behind to review numbers as a CFO.

CTOs, on the other hand, will come from a technical background, although those backgrounds can vary significantly, from IT support to IT consultants. The CTO is a relatively new position, and is often seen as a sort of supporting role within the C suite, although given the ubiquity of ICT in the modern economy, and given the importance of technology to certain sectors, the CTO can actually have a more significant strategic role than, say, the COO.

Of course, not all companies will have need of the XO suite (as it is sometimes known, especially in the US).

Depending on the sector, many companies will have managing directors and general managers without feeling the need for "Chiefs". And there is often an element of vanity to corporate nomenclature.

"A company would want to have a turnover in the region of 50m for the titles to mean what they are supposed to mean, " said O'Donnell. "There can be some vanity to the titles and, for example, it might be silly to call oneself the CFO of a small company."

There is also the fact that, by elevating everybody to a position of seniority, a company can become top-heavy.

It can also devalue the titles themselves, and, for example, in the US a new tier has been created with the advent of the vice-president. Thus, traditional managers become directors, directors become "Veeps" and chief executives become potentates of almost unlimited magnitude.

However, America has also been imaginative in its creation of senior executive positions, and "Chief Evangelist" is a good example of an important strategic position in the new economy (the evangelist is, like the name suggests, somebody charged with spreading the word . . .

and there tends to be a quasiphilosophical element to the role). But whatever a person in the C Suite is called, the reality is that they will, by virtue of being there, have achieved some sort of corporate apotheosis, with only the position of chief executive left to strive for.