On Dragon's Den, entrepreneurs traditionally enter the den before presenting their business proposals.
The entrance is part of the programme's recognisable staging. A contestant walks into the room, approaches the panel of investors, and begins a presentation explaining the business, the requested investment, and the equity being offered. The investors then ask questions and decide whether the opportunity interests them.
This presentation structure gives the programme its distinctive theatrical setting, but the underlying decisions concern real commercial proposals. The investors are not judges awarding a prize; they may offer their own money in exchange for a share of a company. A proposal can therefore end with an offer, a negotiation, or no investment.
The phrase is also central to the show's title. The den is a television set designed to create a focused meeting between entrepreneurs and investors, rather than a literal animal habitat or a competition arena.