Hyperbole comes thick and fast in interim management. Some companies that supply interim managers claim to have several thousand on their books. But what they usually have is a big pile of CVs rather than top executives.

Then there is the mouth-watering pay dangled before interims. But don’t get too excited at talk of £1,000 a day; £500 is much nearer the mark. And being an interim manager is no soft option. From day one of your assignment you will be expected to be some kind of Superman and rapidly achieve results.

There are claims that the public sector is now the biggest user of interims, but this not true — at least not yet, according to Alan Horn, who runs Albemarle Interim Management, part of Vedior, one of the world’s biggest suppliers of interim managers. Some other companies have become prominent in the sector, such as Borden and BIE, but nobody can match Vedior. After the acquisition of Armadillo and Walker-Cox, it has doubled in size and is the undisputed leader.

Supplying interim managers can be a highly profitable business and it is growing fast. “There’s been outstanding growth this year,” said Horn. “In part, the growth of interims has been fuelled by huge changes taking place in UK plc and these are still under way.”

He cited the example of the telecommunications industry. The constant change in the industry has brought a steady flow of business. The break-up of British Telecom and the rapid growth of mobile telephony have reshaped the British industry.

The mobile boom created companies that were hungry to expand and grab market share, goaded on by the need to pay for expensive third-generation licences. They needed interim managers to help handle the dizzy growth.

The privatisation of the railways led to a similar leap in demand for interim managers.

Before privatisation the railways were run by railwaymen, rather than managers. The upheaval has created a new breed of manager and fostered an entrepreneurial culture.

“The industry is now run by professional managers as opposed to railway people,” said Horn. “We deal with the top five rail companies and they are going through change continually. They are always seeking to win bids for new franchises.”

Companies bidding for railway or telecom franchises have a near-insatiable demand for interim managers. They must have a shadow management standing by, ready to run the new franchise should they win it.

But if the former state industries have been a good market for interims, there are now signs that the state sector also needs more.

“Huge changes are taking place there,” said Horn. “It’s a different environment to work in and it’s not yet being addressed. It’s an important area that is becoming very valuable to us.”

Nowhere has the rise of the interim manager been felt more keenly than in the boardroom. Research by Professor Andrew Kakabadse at Cranfield School of Management has shown that the lifespan of directors has declined sharply. “The average expected tenure of a chief executive has fallen by one third in the past two-and-a-half years. A chief executive is not expected to have a lifespan extending much beyond 18 months,” he said.

Interim managers may be called in to help smooth things over after boardroom upheavals. But Kakabadse’s work has shown that relations between the board, chief executive and interim manager can be fractious. “Don’t be surprised if the board is undermining the new chief executive by the second week. You get such rapid change that it is difficult to manage the relations between them all.”

The big question is what is the role of the board in such situations. Kakabadse believes that only bad boards would allow relations between directors and senior executives to deteriorate so badly.

Thankfully, such problems are fairly rare and interim managers earn their keep. Albemarle’s Horn said: “We have to provide interims who are as good as a client company’s best people. It’s certainly not a place for faint hearts. Out of every 100 people who apply to become interim managers, probably six are worth their place.

“Firms that say they have between 10,000 and 15,000 interim managers on their books are talking utter nonsense. They don’t understand the damage they are doing to the industry and themselves. It’s just a great collection of CVs. The industry doesn’t have that many people.”

Large suppliers take great care to make sure that the interim executives they offer fit in well and that the clients get good service. “At the top end there is a clear focus on the quality of the operation,” said Horn. “You have to be a good manager to be an interim manager. Individuals may be spot on with their CVs but that doesn’t take account of all the possibilities. A good interim manager will, with our help, focus on what matters right from the start.

“We won’t do business with a client who will not meet us. Our view is that we will get the individual to focus on the end result. The things that are needed to get there will be agreed with the client and the interim manager. The client has committed to a budget and is not afraid to say exactly what it wants.”

There is still great scope for growth. Each year about £300m is spent on interim managers, small beer when compared with the £6 billion a year spent on management consultants.