Captain Sir Tom Moore believed he would come out of hospital alive and was looking forward to celebrating his 101st birthday, his daughter has said.
His daughter, Hannah Ingram-Moore, said her father had told nurses 'I'm coming back out' and she had laughed and reminisced with him during his final days in hospital.
She also spoke about the difficult time for the family since his death as she revealed details of the Captain Tom 100, encouraging people to take on charity challenges themed around the number 100.
People are being asked to do their bit to celebrate Captain Sir Tom's spirit of generosity from 30 April – what would have been the weekend of his 101st birthday.
"None of us could have planned for what happened," said Ms Ingram-Moore.
"My father definitely did not expect not to be here. That's just a fact.
"But he was 100 and he was a very happy 100.
"He lived those 100 years, and the last year was simply extraordinary.
"How we feel is that we were not expecting him not to be with us and we miss him desperately."
She said Capt Sir Tom would tell nurses: "I'm coming back out, I've got a lot of fundraising to do, I've got my birthday celebration."
Ms Ingram-Moore said: "While he was in those last few days in the hospital I don't think he ever thought he wouldn't come out, he never talks like that."
She added that coming to terms with her father's death was "a massive shift in my emotional state", and said telling the world "felt like an incredible burden".
She said a decision was made to tell people that Capt Sir Tom was not well while he was in hospital.
"As he went to the hospital I phoned my sister and said 'I think we need to start telling people he's not well, I know that's really hard but we have to communicate it because I cannot live with not telling people that he might not be well – I cannot live with myself if I go from saying he's alive to not alive'," she said.
Ms Ingram-Moore added that the family had never lived at their home in Marston Moretaine, Bedfordshire, without Capt Sir Tom.
"I don't think many people realise that. I think they thought he came to live with us later. But no, we've never lived here without him.
"He's in the very fabric of the building, he's all around us."
She said that "we're still a grieving family", adding: "We're sad and sometimes sadder than others, but we're propelled forward by hope and we want (people) to come with us."