Fellowes was joined by singer Lulu, actor Edward Fox and members of Rees' family who gathered at St Paul's Church in the Knightsbridge area of London to celebrate her life on Thursday (27Sep12).
The British star, best known for her role in 1970s U.K. TV series Poldark, lost her battle with pancreatic cancer in July (12) at the age of 63.
Fellowes told the congregation, "She was a fighter. Not for nothing was her nickname hand grenade. I have only had four real rows since I was grown up and two of them were with Angharad. We once emptied a restaurant, when the other patrons started to ask for their bills, or to be seated elsewhere to get away from the noise we were making.
"But, if her fierceness made her a frightening opponent, it was a wonderful quality to have on your side. Because, if there was one thing she was superb at, it was friendship, and not just sympathetic friendship but hard-working, useful, practical assistance."
He also praised Rees for balancing her career with family life, adding, "She was determined that it would be her children who took precedence. She was not prepared to pay the price of being a great actress if it meant that her family would have to pay it with her.
"She was anxious, I think, that she should not be defined, entirely, as the star of a popular series, as one half of a golden couple, as a mother and hostess, although she excelled in all of these."