Former real estate agent Gerard Baden-Clay’s wife and mistress were due to cross paths when Allison Baden-Clay suddenly vanished, a court has heard.

The two women in former Brisbane real estate agent Gerard Baden-Clay’s life were about to cross paths when one of them suddenly vanished, his trial has heard.

The Supreme Court in Brisbane has heard details of Baden-Clay’s double life, appearing as a devoted father and husband to his family while carrying on an affair with a colleague.

Giving evidence, former mistress Toni McHugh wept as she detailed her roller coaster relationship with former boss Baden-Clay on Monday.

Baden-Clay, 43, has pleaded not guilty to murdering his wife Allison Baden-Clay in April 2012.

Real estate worker Ms McHugh said she began an intense affair with her boss in 2008, but he broke it off in September or October 2011 when Mrs Baden-Clay found out.

However, the father-of-three resumed contact in December that year and in an April 3, 2012 email that was shown to the jury, wrote: “I have given you a commitment and I intend to stick to it – I will be separated by 1 July”.

Eight days later, he sent another email: This is agony for me too … leave things to me now. I love you.”

On April 19, the night before Allison was reported missing, Ms McHugh said she “lost it” with her lover after learning she and Allison would be at the same real estate conference.

“You need to tell her,” she told Baden-Clay in a rage.

The next day he told her Allison was missing and to “lay low”, later telling her to “tell the truth” to police.

“I need you to know that I don’t know what’s happened here. I need you to know I love you,” he told her.

Then in a final, secret meeting: “He told me that I would have to fall in love with somebody else … he suspected that things weren’t going to be looking good for him.”

She said they had no contact after that.

Allison Baden-Clay’s body was found on a creek bank on April 30, 2012, 10 days after her husband reported her missing from their home in Brookfield, in Brisbane’s west.

Baden-Clay remained composed while his former lover testified, though earlier shed tears as his sister told the court how obviously in love the couple had been at the start of their marriage.

Olivia Walton said she later became aware Mrs Baden-Clay suffered depression and anxiety.

She said her sister-in-law had difficulty with parenting and “the pressures of life seemed to be too much for her”.

In contrast, Allison Baden-Clay’s parents and best friend downplayed her depression and anxiety, saying her low moods were understandable in a mother of three young children.

Allison’s mother Priscilla Dickie said her daughter “tried everything she could for that man”.

Mrs Dickie, who also broke down in the witness box while giving evidence, said her son-in-law appeared “calm as a cucumber” the day he reported Allison missing.

Earlier, his father Nigel Baden-Clay, a former insurance agent, explained to the court how he organised a lawyer for his son soon after Allison vanished.

He also sent a life insurance claim to Allison’s insurer on behalf of his son within a month of her body being found.

“It’s … in one of the terms and conditions of the life insurance that you are to notify the insurance company as soon as the event occurs or as soon as possible after the event occurred,” he told the court.

The trial continues.