Few things annoy British rail passengers more than late trains. Travelling on dirty trains, however, is one of those few annoyances and Connex, the French company that will run the Luas transport system in Dublin, has had more than its fair share of complaints about poor conditions on its trains operating in London and southern England.

"There is no excuse for dirty trains," said Ms Wendy Toms, chairwoman of the southern England region of the Rail Passengers Council, commenting yesterday on Connex facilities.

"They are trying to do something about it and they have shown a willingness to listen but there is still room for very large improvement," she said.

Connex is the largest private transport operator in Europe, with an annual turnover of €3 billion (£2.4 billion) and 42,760 employees. The company has built its reputation by moving into public sector businesses and running them privately.

"It has redefined the interface between public and private sector," an industry analyst said. "The public sector sets the goals; Connex achieves them with private sector methods. It's part of a broader trend."

Connex manages most of the school bus and internal city bus networks in France, and 17 per cent of the British rail system. Its name was coined seven years ago, when the former CGEA won a contract to run the south-eastern rail line in the suburbs of London. CGEA's directors liked the name so much they extended it to the entire company.

When Connex won the franchise to operate south central and south eastern routes in 1996, it quickly earned a bad reputation among commuters for dirty toilets, poor station maintenance and late trains.

Speed restrictions on all rail routes imposed after the Hatfield disaster did not help punctuality and the fact that the rail system was never designed to transport so many people added to Connex's problems.

One reason Connex lost the franchise to operate the south central services out of London was probably the public outcry over late trains - not always Connex's fault - serving more than 110 million passengers each year on 444 route miles.

Pressed to end uncertainty for passengers and staff, the train operator agreed last year to hand over early to a new franchise and is now bidding to add the strategically important trans-Pennine route linking Sheffield with Manchester to its south-eastern England routes.

It has not been linked to any major rail crashes in Britain, a spokesman said.

Connex is also present in Germany, Portugal, Scandinavia and Australia.

Although Connex is a large company in transport terms, it is dwarfed by its far bigger parent companies: Vivendi Universal, the world's second-largest media conglomerate, and Vivendi Environnement.

Vivendi Universal has a market capitalisation of €57 billion and 250,000 employees worldwide.

Vivendi Universal owns 63 per cent of Vivendi Environnement, which is independently quoted, and owns the Vivendi water company, Onyx waste management and Dalkia, which runs boiler stations for the central heating of large building complexes.

This overall environment group, to which Connex belongs, has an annual turnover of €26 billion. These companies grew out of the original Compagnie Générale des Eaux, founded in 1853.

Contrary to a widespread misperception in France, the CGEA was always a privately owned company. But it expanded by "delegated management" or concessions, that is taking over publicly owned operations.

According to its website, Connex operates 4,000 km of rail lines worldwide, and transports one billion passengers annually.

The company spends €7.7 million on research each year, mainly to develop new transport and information systems, and to adapt existing vehicles.