MALCOLM Fyfield came out of retirement to run the Gleision mine, he has told the jury.
He said poor health, including pneumoconiosis and bad condition, had led him to retire in 2008.
He had sold the Nant Hir mine, which he had run with his brother, and retired.
But he said having worked all his life, he became “bored”. He said when he was approached by MNS Mining Ltd, asking to become their manager he took up his post at Gleision on July 4, 2011.
He said his family did not want him to return to mining.
During his second day of evidence at the trial where he is accused of manslaughter of four men, Fyfield detailed his mining background.
He said his father, grandfather and brother were all miners. He had worked at a number of mines in and around Swansea since taking up mining aged 23.
His role as manager was also discussed. He said he was an "extremely careful" manager and took his safety responsibility seriously "because of the serious nature of the industry”.
He was taken through previous safety plans he had drawn up for other mines.
During their 11-week case, the prosecution have said he should have submitted a Precaution Against Inrush scheme (PAI).
They say that was necessary when a manager planned to break into old workings.
Fyfield said he did not think he needed to submit this PAI plan for this area of Gleision because he had examined the old workings and had seen for himself there was no water in them.
He said during inspections, he had managed to walk to the rear of the coal face and one of these inspections took place the day before the tragedy where four men died.
Because he saw no water, he ordered charges be detonated in the coal face on September 15, 2011.
The prosecution say that blast allowed 650,000 gallons of water to burst through, drowning Charles Breslin, Philip Hill, Garry Jenkins and David Powell.
Fyfield, aged 58, from Caerhenllys, denies four counts of manslaughter.
MNS Mining Ltd, who owned the drift mine near Pontardawe, deny corporate manslaughter.