``It was devastating,'' says Eileen. ``We found out two-and-a-half years after the disaster. Francesa was a dancer. She talked to you with her hands. It was the most horrific thing to have to come to terms with. My husband had a heart attack as a direct result of it. ''
Before boarding the cruiser for a party to celebrate the 26th birthday of Antonio de Vasconcellos, a Portuguese-born financier, Francesca and her boyfriend, John James, had been to a celebratory dinner at the family home in Barnes, south-west London, to mark her leaving ballet school.
Eileen is convinced her daughter was earmarked for a brilliant career. Francesca spent 10 years at Elmhurst Ballet School in Camberley, Surrey, and was among six pupils picked to dance for Princess Diana when she visited the school. She was about to go to Austria to work as a model, dancer and teacher of classical ballet and classical Spanish dance.
As the couple left to go to the party, Francesca flung her arms around Eileen and gave her a kiss on both cheeks. She then popped her head round the corner and chirped: "Bye you bitch!" - it was a term of endearment she used as often as "Love you, mother".
Then Eileen and her husband Vincenzo received a call at 4am from John's father. There had been an accident - John, who survived, was in St Thomas' Hospital, but Francesca could not be found.
``I was numb. From that moment onwards I was incapable of doing anything. It just threw you into terrible panic and shock.''
Life had to carry on, but it no longer semed to mean anything. Living so close to the river merely served as a daily reminder of the tragedy. ``I lived my life through Francesca," said Eileen. "Every dance lesson, every joy, every sorrow we shared together. The loss was devastating and incalculable in any terms. The shock rendered me a physical wreck. I just could not help myself. It was as if a red-hot sword had gone through my heart and I was bent over, deprived of all my confidence and could not pick myself up. One just didn't want to live. Nobody meant anything. You couldn't help your nearest and dearest because you couldn't help yourself.''
The relationship with her husband suffered immensely. After 10 years locked in grief, it is only now that the couple have started to show tentative feelings of endearment towards each other.
The sadness is hard to understand if you have not felt it. ``To lose a child is the worst possible loss. You have given birth to her, you have watched her grow - she was like a beautiful flower. She was not just my daughter, Francesca was my best friend. It very nearly killed me.''
Eileen was helped back from the brink by her other child, the former England rugby captain Lawrence Dallaglio. He stopped playing for 18 months after the disaster, but returned to the game in 1990 to join Wasps Rugby Club, and encouraged his mother to support them.
Not only did the relatives of the victims have to fight to recover from their grief, but they also had an ongoing battle with the authorities. Two years after the disaster a Marine Accident Investigation Branch report found that the failure of look-outs on both the Marchioness and the dredger Bowbelle was the immediate cause of the fatal collision. Four years ago, an inquest found that the disaster had been caused by ``gross negligence'' but the Crown Prosecution Service decided there was insufficient evidence for a prosecution.
Two trial juries had earlier failed to reach a verdict on the role of Captain Douglas Henderson, skipper of the Bowbelle, who was formally acquitted of endangering life by failing to keep an adequate lookout. But on Wednesday Deputy Prime Minister John Prescott bowed to the 10-year campaign by the survivors and relatives of the victims for the right to give their evidence to a public inquiry. A judge will be appointed to investigate safety on the Thames and to advise Mr Prescott as to whether a full public inquiry should be held. The relatives will be allowed to give evidence in public to support their case.
Some of the relatives insist that some vital details of the last moments before the collision have never been disclosed.
``We were all of us plummeted into terrible psychological shock and pathological grief, and everywhere we went we came across a brick wall of silence," says Eileen Dallaglio.
``And every corner and every aisle we took, the doors were being slammed all the time. The injustice was being spelt out in huge words. And all we were looking for was the answers to the questions of how, where, why and by what means our children met their deaths.
"It wasn't [motivated by] any vindictiveness - it was sorrow."
Though absolutely delighted at the news, Eileen is still cautious. She does not just want a full public enquiry held for the sake of it, but she wants action to be taken on the lessons learned.
``The huge question has to be asked `why did it take that long?' And why were these people treated in such an appalling manner? It was as if our children had a right to die. And that's not right. ''
A memorial service for the victims of the `Marchioness' disaster takes place at 11am at Southwark Cathedral in South London today.