Wife-murder accused Rob Packham has come out guns blazing in a bid to poke holes in the state's case against him.

The 58-year-old businessman took the stand for the first time at the high court in Cape Town on Monday.

He explained his movements and peculiar acts – such as switching off his work cellphone and calling his colleague at a beverage production company to cover up for him – on the day his wife of more than 30 years, Gill, disappeared.

A calm and eloquent Packham took the witness stand and told the court what led to him disclosing his extramarital affair to his wife.

"My daughter had known about my affair for some time and she was encouraging me to disclose it to my wife," Packham said.

He said before disclosing the affair in October 2017, he first booked counselling and later he and his wife attended different sessions.

"I think we were making progress before Gill's death," said Packham. "It was a difficult process but we were making progress. All sessions were difficult because it was full disclosures. [They were difficult] for me and for Gill to receive the information. Some hurt her … but it was definitely constructive."

He said there was an impasse between him and Gill on the evening of February 21 2018, ahead of her disappearance the following morning. Packham said the bone of contention was his work trip to Johannesburg the following day.

"She had trust issues. It wasn't exactly resolved, we agreed to disagree," said Packham. He said Gill raised the issue the following morning and threatened to call the CEO of the company he worked for. He told her "not to be silly".

Packham said he left his Constantia home at 7:30am – about 30 minutes after his wife had left – and went shopping for a car for her in order to surprise her on her birthday.

"It was something that had been a family joke, I knew [her car] was 20 years old and had to be replaced and wanted it to be a surprise to her," he said.

He said he told one of his colleagues at work to tell Gill that he had been in since 7am because he did not want Gill to find out about the surprise. He told the court that he had two cellphones – a work phone and personal one.

"Gill was in the habit to track me. That morning I didn’t want her to know what I was doing," said Packham. "She would phone me in my car and ask me to take a picture."

He denied killing Gill.

According to the state, Packham allegedly killed her, put the body in the boot of her car and set it alight at the Diep River railway station in February 2018.

He was allegedly tripped up by licence-recognition cameras showing him driving Gill's BMW, while cell phone towers indicated that he drove around Constantia on the day of her disappearance.

Gill's charred body was found in her car.

The trial continues.