BBC Two originally broadcast the British programme Dragon's Den.
The series launched on BBC Two in January 2005, placing business pitches and investment negotiations in the channel’s factual and entertainment schedule. BBC Two was long associated with documentaries, factual programming, comedy, and specialist subjects, making it the original home for the format.
Dragon's Den later moved to BBC One, where it reached a broader mainstream audience. This change can lead to answers that identify BBC One as the show’s original channel, but BBC Two is the historically correct launch broadcaster.
The channel is part of the British Broadcasting Corporation, the UK’s public-service broadcaster. International versions have appeared on entirely different networks, so the answer applies specifically to the British edition named in the question.