Princess Lilian was "a credit to Swansea", her first cousin Barbara Davies, who was also born in the city, told ITV News.
"She had an exciting life. While living in Stockholm, she did have a degree of privacy."
"From my conversations with people in Sweden they were in high praise of her conduct."
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The peer will attack Prime Minister Theresa May for failing to represent the 48% who voted in favour of Remain.
Paul Flynn, MP for Newport West, will open the debate in Westminster Hall.
It will represent another boost to the region, after the announcement Deca Sealand was chosen for a repair hub for defence aircraft.