Every schoolchild knows who is responsible for the pound's regular rollercoaster rides hordes of greedy foreign speculators ratcheting up elephantine bonus payments by persecuting small currencies. Probably they do most of the trading by mobile phone from their Lamborghinis.

Well, uhm, not quite.

In truth, the vast majority of trading is done right here in Dublin, by Irish men and women, whose annual paycheques never get into six digits. And it's often at the behest of customers; companies exporting to or from Ireland.

There is a small number of Irish pound players in the foreign exchange market, and they all represent large financial services companies.

In all, there are three types of "market-movers", people that have enough power to change the price of the currency in any significant way.

First, there are the Irish banks. The big three Ulster Bank, Bank of Ireland and Allied Irish Banks run their foreign exchange operations from the IFSC in Dublin's dockland, with Citibank as the fourth "market maker". Smaller players, such as Anglo-Irish or National Irish, are also based either in the centre or elsewhere in the city.

These traders about 10 in total dominate the market, accounting for around 80 per cent of all volume on any one day. They buy and sell on behalf of companies, and on behalf of their own financial institutions.

Even if, for example, a German company decides it wants to buy or sell pounds, its financial service provider will usually contact an Irish bank to do the deal.

For these traders almost all men the working day begins at 7.15 a.m. They scan the financial information screens for overnight news and trends, and steady themselves for the first prices at 8 p.m.

There is no pit, with dealers screaming orders at each other or into phones; everything is done on a sort of text version of the telephone. When a bank is contacted by another financial institution, it must give two prices, one at which it will buy, another at which it will sell.

Ideally, the business is about matching a customer who wants to sell with a customer who wants to buy, and pocketing the difference. Ideally also, a trader will balance the books by the end he or she will have sold and bought the same number of pounds and start each day with a fresh sheet.

Often, however, things are complicated by the variety of different types of deal that customers and banks can make, and traders sometimes carry plus or minus totals from one day to the next.

For the dealers that start early, the day usually ends at 5.30 p.m. or 6 p.m. But the banks can go on trading pounds for another five hours, and on busy days the traders work right through alongside later-starting colleagues.

In the course of a normal day, each of the top three banks will usually trade more than £100 million; any day in the past week it was probably double that volume. Typically, half of this is driven by companies, customers of the banks, seeking to buy or sell pounds; the other 50 per cent of transactions are made on behalf of the banks themselves.

The typical daily volume in the pound is about £500 million. While this sounds like a lot, and comes to more than £120 billion a year, it pales into insignificance compared with the £600 billion traded every single day between the dollar and the deutschmark.

It is a young person's game; the stress levels are high and family life is likely to take a back seat whenever there's a currency blip. Most traders are aged between 25 and 45.

But while the pay is nowhere near Wall Street level, the dealers are well rewarded. A young trader could expect to have a base salary of £40,000, with a performance-related bonus bringing the total to £80,000. More senior traders can command salaries of £80,000, with a bonus pushing them towards £120,000.

This is still a good deal from their company's point of view. The traders do the same job as their New York counterparts, just as competently and as conscientiously, and typically make at least £1 million a year in profit, for a lot less money.

Second, at times of particular interest, other players enter the market. In Britain, seven or eight traders keep a close eye on the Irish currency, and trade whenever they see a profit to be made. In the United States, Germany, France and Japan, another 20 or 30 dealers in giant institutions like Chase Manhattan and Deutsche Bank cast an occasional eye on the pound. Any clear indication of how the currency is moving and they move, swiftly and in volume.

A third group of potential market movers are the insurers' investment managers, such as those in Irish Life and Norwich Union. While they are not regarded as players, they have the power to move large amounts of currency at any time, hedging their investments.