After which series did Duncan Bannatyne leave BBC's Dragon's Den?

Duncan Bannatyne left BBC's Dragon's Den after series 12. He had been one of the programme's original investors and was part of the panel from the show's launch in 2005.

Bannatyne built a business empire that included health clubs, care homes and hotels. His time on the programme made him known for challenging entrepreneurs about valuation, profit and the practical risks of running a company.

His departure was part of the programme's continuing changes in investor line-up. The show retained some established dragons while adding new figures, meaning that individual series are often used to mark important transitions in the panel's history.

The wording “after series 12” identifies the point at which Bannatyne stopped appearing as a regular dragon. It is not the same as saying that he joined in series 12 or that the entire original panel left at that time.