Peter Jones has appeared as a dragon continuously since the British series began in 2005.
Jones is a British entrepreneur and businessman whose interests have included technology, communications, property and retail. He joined the original investor panel and became the only dragon to remain continuously associated with the programme from its launch through its subsequent series.
The panel itself has changed repeatedly. Early and later dragons have included Duncan Bannatyne, Deborah Meaden, Theo Paphitis, Richard Farleigh, James Caan, Kelly Hoppen and Touker Suleyman. Their different backgrounds give the programme a changing mix of questions, valuations and investment styles.
Continuity is the key distinction in this question. Other well-known dragons were present in the early years, but they left the regular panel or appeared for limited periods. Jones's uninterrupted tenure is why he is often described as the show's longest-serving original dragon.