Speaking ahead of attending the event in London, Mrs Long said it was an historic occasion.
“My best wishes and congratulations go to Their Majesties King Charles III and Queen Camilla for their coronation day,” she said.
“It is an historic occasion, with the first crowning of a new monarch in 70 years.
“King Charles follows in the footsteps of a wonderful example of a sovereign, her late Majesty Queen Elizabeth II, who was loved and respected across the world for her service in the role, which was evident at the outpouring of emotion at her passing.
“Much has changed in these islands and across the Commonwealth and globe since Queen Elizabeth II’s coronation.
“The new King has shown an active interest in current affairs and in nurturing and supporting progress, whether our peace-building efforts locally or his highly respected environmental work globally, as well as his support for young people and creating opportunities for them via the Prince’s Trust.
“That commitment to duty and service is to be admired, and I send the King and Queen my best wishes as they are crowned.”