Before moving to BBC One, the British TV programme Dragon's Den was broadcast on BBC Two.
Dragon's Den began on BBC Two in 2005, where it developed its identity as a business-focused factual entertainment programme. The channel was traditionally associated with documentaries, arts, comedy and specialist factual programming, making it a natural home for a show centred on entrepreneurs, company finances and investment negotiations.
The programme later moved to BBC One, giving it access to a broader mainstream audience. That change is distinct from the programme's launch and from changes to the investor panel. A channel move does not mean that the format itself changed nationality: the British series remained the UK version of a format originating in Japan.
Viewers can also confuse BBC Two with BBC Three because both have carried factual and entertainment programming. However, the established original home of the British Dragon's Den series was BBC Two. The relevant answer is the channel, not the BBC as a whole.