Princess Diana was determined to live up to the title of Princess of Wales, the former Lord Lieutenant of South Glamorgan said.
Sir Norman Lloyd-Edwards said an obvious way was by going to Welsh international rugby matches.
He escorted her to many and said she started bringing her sons, princes William and Harry, adding she wanted them to “get to know Wales and love it like she did”.
It is 20 years since Princess Diana died in a car crash in France.
The princes will be marking the anniversary in private, but other public services will take place across the UK.