OLYMPIC athlete Dame Kelly Holmes has described the "heartbreaking" experience of losing her mother to blood cancer as she campaigns to raise awareness of the disease.

The double gold medal winner spoke out as it emerged that more than half of British adults could not name any symptoms of the condition, despite it being one of the most commonly diagnosed cancers in the UK.

One in 19 people will be diagnosed with blood cancer, according to the charity Bloodwise, while it is the third biggest cause of cancer deaths, killing more people every year than either breast or prostate cancer.

Dame Kelly described how her whole family was shocked when her mother, who she called Mother Dear, was diagnosed with myeloma at the end of 2014.

She had been suffering bad colds and pneumonia during recent winters, along with back pain but, "Me being a sportswoman, I was like: 'yeah, have a massage. You'll be fine," Dame Kelly told the Press Association.

An X-ray at Tunbridge Wells Hospital in Kent, where she had worked for many years as a nursing assistant, showed she had broken ribs, which Dame Kelly described as "weird" as her back pain had been put down to her dog pulling on its lead.

Subsequent blood tests showed up abnormalities, before a bone marrow biopsy showed she had myeloma.

"When she was diagnosed it was a big shock, because, one, I think no one had heard of myeloma. We didn't really know what it was or understand what it was. And secondly, to say 'you've got cancer', isn't a thing you want to hear with anyone," Dame Kelly said.

"My mum always had a real strong mind and was positive - really, really positive about it. Mainly because the consultant was brilliant, and said, 'these are all the treatments, we can just keep trying, If one doesn't work we'll go on to the next one'."

Her mother underwent chemotherapy and had a stem cell transplant, which initially made her feel much better, but she died suddenly while in hospital on August 7 last year, aged 64.

Dame Kelly said it was "brilliant" to be asked to be the official ambassador of Janssen UK's Make Blood Cancer Visible campaign so she can make more people aware of the killer disease.

She said: "The reality is that so many people that you walk past in the street, so many people of your friends and family, will get a cancer of some description.

"The thing is with others, there may be more obvious signs that people know to look out for, whereas with blood cancer, how do you know?

"You break a rib, she thinks it's the dog. You don't hear of it.

"And the thing that we're trying to bring with the Make Blood Cancer Visible campaign is the realisation that, actually, so many people could be walking around with an illness who won't know."

Describing the struggle her mother - who was 17 when she had her - went through, she said: "Mum was quite a strong character.

"Watching the deterioration and watching someone cry who never normally cries is quite heartbreaking."

Talking of her childhood, which saw her live in a children's home until she started primary school, she said: "Mum struggled. (I was a) mixed race kid growing up in white Kent, and she was on her own.

"My granddad - her dad - said she couldn't look after me until she could prove she had a stable job and stability.

"I realise how much she fought to keep hold of me - that made me realise how strong a character she was."

Dame Kelly, who won gold in both the 800m and 1500m at the Athens Olympics in 2004, described how hard the bereavement has been.

"I've struggled with it badly," she said.

"I'm quite open on my social media about how I'm not coping with it, but equally I think it's important to get the message out there that there are so many people out there that are going through this. Especially with blood cancers, that are not so well known.

"It's best to be aware of it because there may be signs and symptoms that have been missed.

"But also on a positive note, there is hope. You can prolong life, and actually you can prolong life a lot more if you see the symptoms earlier. If you're not aware, you don't know."

Blood cancer is the fifth most common cancer in the UK, made up of more than 100 different sub-types including leukaemia, lymphoma and myeloma.

It affects more than 240,000 adults but patients often require more visits to their GP before diagnosis than with other cancers, leading to concerns that these delays can lead to patients being disadvantaged and having less chance of survival.

Dr Alberto Rocci, consultant haematologist at Manchester University NHS Foundation Trust, said: "Early diagnosis of blood cancer is vital for improving patient outcomes.

"However, blood cancer doesn't always present with clear-cut symptoms and it may be confused with less serious illnesses.

"It is important to discuss with your GP any unusual symptoms that last for more than a couple of weeks. An early diagnosis can drastically improve the length and quality of life."

A number of short films featuring Dame Kelly and other people whose lives have been affected by blood cancer can be seen on the website www.makebloodcancervisible.co.uk.