Speaking to the Sunday Times, he said 92-year-old Quintin had left a note saying his “system is closing down” and he had “no alternative”.
Davis’s brother had texted to break the news while the Radio 4 host was at his wedding reception in July last year.
The presenter made an impromptu speech telling the guests his father had died.
He said the occasion turned into “a very warm-hearted, supportive, reflective day” – he did not tell the guests it was suicide until later.
Davis, known for hosting TV’s Dragons’ Den and BBC Radio 4’s PM programme, married Guillaume Baltz in a follow-up event to their civil partnership ceremony in 2012.
Quintin was very supportive of his son’s relationship, making a “proud and loving” speech on that occasion.
But his wedding in London only included a small number of guests not invited to the first event, including two dozen friends and neighbours.
During the ceremony, Davis said he received a message from his brother Roland telling him to “call ASAP”.
When he told him their father had died, Davis hung up and gave his husband the news. Davis called back five minutes later, and learned Quintin had taken his own life.
But messages from Roland and his other brother, Beric, encouraged Davis to continue the day.
Davis told his guests: “We’ve just had some news. My father died. But I don’t want you to be alarmed. He was very elderly and it was definitely time.
“There’s actually nothing we can do. So I’m going to propose that we carry on.”
It was at work the next day when his colleagues asked how his wedding was, Davis said he “burst into tears”.
Davis said Quintin had emailed his three sons the previous year informing them of his intention to kill himself.
But speaking to Sunday Times journalist Decca Aitkenhead with his family’s consent, he said he would never know why his father chose his wedding day to do it.
He said: “We’ve all speculated on what the hell was going on in his head… there’s no good day, is there? And I know he didn’t do it to spoil our day.”
Several notes were discovered alongside Quintin’s body.
He wrote a note for his wife, Davis’s mother Hazel, who was in a care home, telling her how much he loved her, and three identical notes for his sons.
Another handwritten note read: “To all my family, I am so sorry – so, so sorry – to spring this on you. But it is the best outcome.
“My system is closing down and I am on the verge of a mental breakdown – ie, I am going mad and physically falling apart. I really have no alternative. Thank you all for being such a wonderful family.”
Quintin separately left a note pointing out he had “at no time been helped in any way in deciding to take my own life”, and that he “perform(ed) this action because I wish to maintain my autonomy”.
He left a bag of fresh clothes for his wife, “so she could be topped up at the care home”, and cash for the gardener’s weekly wages.
Davis’s father and his mother, originally from South Africa, came to the UK after meeting at university, and had been together for 65 years.
When his mother was admitted to a care home during the Covid-19 pandemic after she started to show signs of dementia, Davis said he noticed his dad had also started to deteriorate.
Quintin was diagnosed with bowel cancer, and his heart was failing.
Davis said his dad had “felt very bad” that he could not look after his wife.
He said: “Having been together for 65 years, suddenly being on his own at home was a big deal… I think he felt guilt at not being able to look after her.”
Read from: https://www.bbc.com/news/uk-66279286