Gareth Edwards recalled events leading up to the tragedy

They had gone out for the day with four children and their young baby and had set up a picnic near a railway bridge in Borth, where the girls were playing when they were hit by a high-speed train.

The couple - who were released on bail - were expressionless when the jury at Swansea Crown Court returned its verdict. Judge Mr Justice Richards adjourned sentencing for reports.

Outside court, the solicitor representing Tony Allcock, whose daughter died in the incident, said his client would be claiming compensation against the Edwards.

The verdict, he said, "did not ease the feelings of grief in Kymberly's family following the tragic loss".

Memorial: Flowers laid at the scene of the accident

Detective Chief Inspector Miles Flood of British Transport Police said there had been a lot of sympathy for the defedants.

"But," he added, "this was an important message that needs to be got across to people.

"If you do take children anywhere near a railway line, you do not allow them to play on that railway line because, as we have seen in this case, it leads to tragic consequences."

On Thursday, the jury heard Mr Edwards - Sophie's stepfather - say the tragedy would haunt him for the rest of his life.

'Keeping watch'

When asked if he blamed himself for their deaths, Mr Edwards replied: "That is a very difficult question for me to answer, particularly in these circumstances.

"What happened on that day is something I will never forget and will live with me for the rest of my life."

Leighton Davies QC, prosecuting - who accused the Edwards of "staggering negligence that must be marked by a criminal conviction - said they had failed in their duties.

Kymberly Allcock, one of the girls who died

He said: "Would a reasonable, careful parent leave his child out of his or her sight for a second in that vicinity?"

"The fact that the children were on the line means that you and Amanda could not have been keeping a watch on them every second of the time. You must have failed in your duty as a parent."

Mr Edwards - a deputy manager at a cash-and-carry store - said: "The children were playing in the usual way children play," he said.

The court was told that the train driver could not see the girls until the train was upon them because they were lying in a trough on the line.

Amanda Edwards shouted to warn the two girls

Earlier evidence suggested that they had been playing on the bridge for up to 30 minutes unsupervised.

But Mr Edwards told the court the children were never out of his sight for more than three minutes at a time.

"They were coming to us and we were giving them a drink of pop now and again and some crisps," he said.

"Amanda and I were sitting side by side on the embankment with the baby and we became aware of a noise," he recalled.

On Wednesday, Mandy Edwards broke down shaking and crying as she described the moment when she says she realised the children were on the railway bridge.

She said she heard shouting, looked up and saw the train coming.

There can be no winners from a case like this

Ceredigion MP Simon Thomas

Seeing her daughter Sophie and her eight-year-old friend Kymberly lying on the track she shouted to them to get off the line but it was too late and the train hit them.

The girls' brothers Christopher George, nine, and 11-year-old Matthew Allcock, managed to jump to safety as the train roared past.

MP for Ceredigion Simon Thomas later said the decision to prosecute had been a contentious one.

"The guilty verdicts must now be tempered by humanity, as Mr and Mrs Edwards lost their own child.

"I hope that Mr and Mrs Allcock will be able to use the discovery of the truth of their daughter's death to help heal their grief.

"There can be no winners from a case like this."