Peter Jones remained on every British Dragon's Den series from its 2005 launch.
Jones joined the original panel when the programme began and became its longest-serving investor. His business interests have included technology, telecommunications, retail and leisure, giving him a broad range of experience when assessing pitches.
The other original Dragons did not all remain throughout the run. Duncan Bannatyne left after the 12th series, while Doug Richard and Simon Woodroffe departed much earlier. Rachel Elnaugh was also replaced after the opening series.
“Original Dragon” can refer to anyone in the launch panel, but the question asks about continuous participation across the British series. That distinction makes Peter Jones the single answer rather than another investor associated with the first season.