Paul Costelloe, the Irish fashion designer known for dressing Princess Diana, has died peacefully in London at age 80 after a short illness.He launched his own label, Paul Costelloe Collections, which showcased his work at major fashion events like London Fashion Week and New York.He was appointed the personal designer to Diana, Princess of Wales, from 1983 until her death in 1997, creating elegant evening wear and other designs reflecting luxury and innovation.