Just to mention that Joan will be appearing in ITV's special tribute show 'Our Cilla' which screens Christmas Day at 10:45pm on ITV1
Speaking on Our Cilla, a tribute programme celebrating the late star her son Robert also said she was troubled by ailments commonly associated with old age.
Her hearing had started to go so she had to start wearing hearing aids. Typical of my mum, she wouldn't wear them. The thing that really affected her physically was her arthritis,
– ROBERT WILLIS, CILLA'S SON
Willis, who was also her manager, talked about the last day he spent with his mother at her home in Spain.
I'd gone for a jog, gone for a swim and stuff. She was sitting around having a glass of champagne, killing herself laughing at Jeremy Kyle - without the hearing aids obviously - so blaring out across Marbella.
We hung out and at about 1 o'clock, I said I was going to do a shop. I said goodbye and that was the last time I saw her.
– ROBERT WILLIS, CILLA'S SON
Black died of a stroke on August 1 after falling and hitting her head at her Spanish villa.
The 72-year-old was sunbathing when she lost her balance, fell, and hit her head, which knocked her unconscious.
Black never remarried after losing husband Bobby Willis to cancer in 1999.
The couple, married for 30 years, had three sons and a daughter, Ellen, who died after being born prematurely.
Willis revealed her heartache over his father's death.
"It was so difficult for her just to acknowledge it," he said.
His younger brother Ben added: "Dad was 57 when he passed away, and that hit everyone. It knocked mum for six."
On the same subject, Joan Collins revealed: "She was looking for a boyfriend.
"I'd say, 'I think I might know someone' and she'd say, 'No, I don't really want one - I can't forget Bobby. Sometimes I feel like I want one and sometimes I don't'."
ITV's hour-long celebration hears not only from Black's family, but also fellow showbiz friends including Beatle Ringo Starr, Sir Cliff Richard, Lord Andrew Lloyd Webber and Paul O'Grady.
Alongside rare interview and archive footage, there are candid and surprising insights.
Comedian O'Grady shared an anecdote about her hair.
"The colour she used to use was called 'Ginger Twist'. She called me up in a blind panic - they'd discontinued Ginger Twist!
"Everywhere in the world I went I'd go in and ask for it. They'd look at me with my white hair and I'd say, 'No, it's not for me, it's for me friend'."'
Born Priscilla Maria Veronica White in Liverpool, Black had spoken of how she would die happy if she were to pass away before any illness could rob her of being able to enjoy life.
She became one of the nation's favourite entertainers after transforming herself from a successful singer in the 1960s to the front woman on shows such as Blind Date and Surprise! Surprise!
Starr, a friend for 57 years, lauded the entertainer for remaining down to earth and not putting on "any airs or graces". "She was a really good friend, you could always call on her. We made each other laugh; we had the same sense of humour," he said.
"She was one of the people. She didn't change her accent, didn't put on any airs or graces."
Our Cilla is broadcast on Christmas Day at 10.45pm