But Clague's lawyer Michael Lloyd disputed that version of events and said what happened was "acceptable conduct in the context of an intimate relationship".
"His defence has always been that it was in the context of Ms Denham absolutely going off her rocker, being loud, hurling expletives of abuse within earshot of the neighbours and the child," he said.
The 49-year-old moved to the UK last August after landing the job of headmaster at 500-year-old Bromsgrove School in Worcestershire.
Over the next two or three days he will hear allegations about what began the bitter breakdown of his relationship with the complainant, who brought the private prosecution against him.
On September 10, Ms Denham returned to their North Shore property to find Clague packing camping gear for the weekend, Ms Dyhrberg told the court.
"They had argued earlier that week and things hadn't cleared."
Ms Denham began unpacking the vehicle and the pair met in the doorway of the garage where the alleged altercation developed.
Ms Dyhrberg said in a police interview, which would be played for the jury, Clague told investigators he "just lost it".
But Mr Lloyd said his client's actions had been done "in a pleading way" and a slip on the polished floor had caused him to overbalance and push Ms Denham backwards on to the step.
Mr Lloyd said the complainant had launched several media campaigns against his client and was out to destroy the man with whom she was in a relationship for six years.
Mr Lloyd said she also had a grudge against Kristin School, where he was formerly executive principal.
"She has actually developed over the years this persona of a victim of domestic violence that's completely fictional," Mr Lloyd said.
Ms Denham will give evidence this afternoon.
The trial before Judge David McNaughton and a jury of seven men and five women is expected to finish before the end of the week.
