Source: Facebook / A Fight Against Neuroblastoma.
Jessica, who has been fighting stage four neuroblastoma for 13 months, but has now been given just weeks to live after Andy and his partner Nicki Prendergast decided to stop treatment in a bid to allow her to enjoy whatever time she has got left.
"This is the true face of cancer," says Andy, who documents his daughter's battle on Facebook.
The father of a terminally ill 4-year-old girl who died yesterday has posted a heartbreaking tribute to his "little princess" whose portrait made her a worldwide symbol for children battling cancer.
A black-and-white photograph of Jessica Whelan grimacing and arching her back in pain because of neuroblastoma, a rare and aggressive cancer that attacks the nervous system, moved many thousands to tears.
The 4-year-old, from Oswaldtwistle, Lancashire, was diagnosed with stage four neuroblastoma in September last year and died yesterday morning.
Andy Whelan and his daughter Jessica. Photo / Facebook
Her father Andy, who took the photograph that captured Jessica's bravery and the "darkness that is childhood cancer", has today written a farewell to his daughter on the Facebook page set up to highlight her plight.
Her death came just a week before a debate by MPs sparked after 115,000 signed a petition set up by her family.
In his message for Jessica, written hours after she died, Whelen said: "I am not ready to let you go Jessica, you are my little princess. You are the most amazing, strongest and bravest little girl and I am blessed to be your daddy.
"The bond me and you share is truly amazing, you always were a daddy's girl, often only calming when I wrapped my arms around you. I'm sorry I couldn't protect you from this evil world baby girl, I'm sorry you had to suffer the way you did.
"I miss you so much baby girl, I miss your voice, I miss your smile, I miss you wrapping your arms around my neck as we cuddle. I miss your spontaneous statement of 'I love you Daddy', a statement you came out with several times daily. I miss you Jessica, tears rolling down my cheeks and wetting my pillow as I think of you and the bond we shared.
"Goodnight my beautiful angel, please come and give me a cuddle as I sleep xxx".
Jessica spent a year of her four-year life battling the cancer that would rob her of a future.
Generous members of the public moved by her plight raised £97,000 ($172,000) to give the little girl the chance to enjoy the last few weeks that she had to live.
Jessica's family had aimed to raise £20,000 through the GoFundMe site, but the target was smashed in a matter of hours after the photograph - which her father described as the "true face of cancer" - was published on Jessica's blog.
More than 4300 people pledged money to the cause, leaving heartfelt messages of support for the family. Andy Whelen said the family had been "humbled" by the response.
He said they "flew through" their savings when Jessica was diagnosed and that the money raised was a "massive help" in covering the likes of transport and food costs.
He told MailOnline: "It has been absolutely overwhelming. It is quite hard for us to comprehend what is being donated."
The family closed the fundraising page two weeks ago when it became clear Jessica's health was deteriorating quickly.
In another display of support, 115,000 have signed a childhood cancer petition demapnding MPs debate how its treatment should be more of a priority to the NHS. It will be debated on Monday, November 28.
Whelan said he has received more than 3000 emails - along with Facebook messages and texts - from all over the world since the photograph was published.
