Two Thomas Cook employees are standing trial in Corfu over the deaths of two children.
Six-year-old Robert Shepherd and his sister Christianne, 7, died in October 2006 from carbon monoxide poisoning at a holiday apartment.
They were found with very high levels of the gas in their bodies.
Their father Neil Shepherd, 38, of Horbury, West Yorkshire, and his girlfriend, Ruth Beatson, 28, were also in the apartment but survived.
The family were on holiday at the Louis Corcyra Beach Hotel at the time of the incident.
The couple only became aware the children had died in the bungalow after they were treated for the effects of carbon monoxide poisoning.