If you are still wondering why CIE's train drivers engaged in their 24-hour unofficial stoppage this week, don't worry, you're not alone.

There is no simple reason to explain why they stopped work on Tuesday only to agree a short time afterwards to advance the industrial relations process according to a formula suggested by management the previous Sunday.

Nothing changed in that 48 hours between the strike and the decision of the drivers' unions to continue talking to Iarnrod Eireann under the auspices of the Labour Relations Commission.

No fresh talks with management took place. No new proposals were made.

Yet, on Thursday, having promised "a winter of discontent" in the wake of the strike, the National Bus and Rail Union (NBRU) general secretary, Mr Peter Bunting, suddenly declared: "Things are looking good. We have issued a positive statement and hope that is reciprocated by a change in mind-set by management".

Threats of further disruption unless the CIE chairman, Mr Brian Joyce, withdrew controversial remarks made last week had also been toned down. SIPTU's Mr Tony Tobin said the chairman's remarks were unhelpful but "everyone has to move forward in a positive way". "We're pleased with the progress made," he added.

The stoppage, then, appeared to have been nothing more than a bit of muscle-flexing by the unions. It served a purpose in strengthening their bargaining position before the next round of negotiations.

Mr Bunting does nothing to undermine this view by describing the strike favourably as "a catalyst". He says: "It was helpful in the sense that it has given a strong signal to both sides that they have to redouble their efforts to resolve the situation."

But if Tuesday was just a show of force by the unions, it would be wrong to think Iarnrod Eireann was the sole, or even the main, target. That was more likely to have been the breakaway rail union, the National Locomotive Drivers' Association (NLDA), headed by Mr Brendan Ogle.

Of the players in the dispute, it was this organisation - at war with SIPTU and the NBRU since pay negotiations began two years ago - which had most to lose by the stoppage going ahead.

A cross-union grouping of drivers with no official standing in the talks, the NLDA had proved to be the most militant representative body. In January 1997, it supported a one-day mass demonstration in the capital of bus and railworkers, which had originally been called by SIPTU and the NBRU. Mr Ogle condemned the two unions for subsequently cancelling the protest, because of fears that CIE might take legal proceedings for being in breach of the 1990 Industrial Relations Act.

In the end, about 2,500 CIE workers participated in the action.

Last July, the NLDA co-ordinated its own one-day stoppage of train drivers. In a direct challenge to the official talks process between management and the two recognised unions, it brought inter-city services to a halt and called for Iarnrod Eireann to start a new series of negotiations with it.

SIPTU and the NBRU called on members to work normally, accusing the NLDA of pursuing "another agenda".

Sources close the negotiations believe Tuesday's stoppage was a calculated response to the NLDA's challenge to the authority of SIPTU and the NBRU. As one source put it, the two unions wished to prove to the workers they were "just as tough" as the unofficial group.

Mr Ogle, who claims to have 118 members in the group, says: "The main rationale behind the stoppage was to attempt to put our members in a position that we would lose strength, having got members from SIPTU. But we have not lost a single member as a result of the disruption."

He claims the NBRU and SIPTU held a meeting three weeks ago "to draw up a strategy to eliminate the NLDA. The seeds of Tuesday's disruption were sown at that meeting."

He says the unions had been looking for an excuse to call for a work stoppage and "that excuse came in the form of Brian Joyce's remarks".

In a speech delivered last week, Mr Joyce called on the Government to state unequivocally that it would not interfere in the company's push to conclude the negotiations. He said the reluctance of successive governments to countenance a disruption to the service was always a trump card.

Within days, the NBRU and SIPTU were calling for Mr Joyce to retract his remarks or resign. Mr Bunting claimed there was "a huge amount of anger" at grassroots level about the remarks, lending towards disruptive action which neither union was capable of stopping.

But Mr Ogle says: "It's totally disingenuous to suggest that the disruption was a result of Brian Joyce's unfortunate and intemperate remarks. Those remarks will soon be forgotten by both unions."

Iarnrod Eireann management is frustrated by the union infighting and places the blame for the disruptions firmly on Mr Ogle's organisation. The company's human resources manager, Mr John Keenan, says: "The development of this group has the potential to undermine the normally good relations between staff, unions and ourselves."

Unless a truce is called between the representative groups further unofficial action remains possible. Inevitably, as was the case this week, the main casualty of any disruption will be the public.