In the mid 1980s, HIV/Aids terrified the world because of a lack of understanding, as well as misinformation.
In April 1987, Princess Diana opened the UK's first purpose built HIV/Aids unit that exclusively cared for patients infected with the virus, at London Middlesex Hospital.
In front of the world's media, Princess Diana shook the hand of a man suffering with the illness.
She did so without gloves, publicly challenging the notion that HIV/Aids was passed from person to person by touch.
She showed in a single gesture that this was a condition needing compassion and understanding, not fear and ignorance.
John O'Reilly was a nurse on the ward at the time of the Princess of Wales' visit.
He spoke to Witness about a landmark moment in the fight against HIV/Aids.