Ian Lazenby, 52, made the threat when he collected the children from his mother-in-law Barbara Lock's home to take them to the zoo. Mrs Lock, of Horndean, Hampshire, told the inquest she had a 'nagging doubt' that the zoo trip would not take place when he took the children away on 21 January. Five days later Mr Lazenby, of Bordon, Hampshire, was found dead with Princess Heidi, nine, Kelly, six, and Rachel, two, 250 miles away in south Humberside.
A tube led from the exhaust pipe into the car, the coroner, Peter Gladwin, was told. Dr Christopher Milroy, a Home Office pathologist, said the pink colouration of the bodies suggested carbon monoxide poisoning.
The inquest is expected to last three days.