The BBC's Panorama programme is to air a documentary featuring the late Tessa Jowell, who died this month, aged 70.
It will follow her final days with brain cancer as she fought a campaign to improve care for cancer patients in the UK.
The former culture secretary was filmed alongside her daughter Jess as she lobbied the government.
Jowell's demands for funding changes lead to a pledge from Health Secretary Jeremy Hunt to carry out her proposals.
These included giving more access to trials and treatments for cancer that had been underfunded over previous years.
Dame Tessa also volunteered to share her health data with a universal cancer databank and wanted more people to do the same.
After her death the government agreed to donate £20m to the Tessa Jowell Brain Cancer Research Mission, doubling funding to £40m over the next five years.
She was diagnosed with a malignant brain tumour in May 2017.
Her tumour - Glioblastoma Multiforme - is the most common and deadliest brain tumour - three in four people diagnosed with her type of brain cancer are dead within a year.
Despite this, it has received less than 2% of research funding and has had no significant new treatments for 50 years.
Brain cancer is becoming more common, and the UK has one of the lowest survival rates in Western Europe.
Her daughter, Jess, said in the documentary: "The only time I've seen mum cry since she got ill, she was sat in the waiting room and had what she described as the absolutely heart-breaking realisation that those who had that privilege of access or income may well live longer because of that, and those that didn't may well die much sooner because of it.
"And in her words, that is just the most despicable example of inequality. In those moments, her mission was really identified."
Tessa Jowell: Her Last Campaign will air on Monday 4 June at 7.30pm on BBC One.