Which Dragon co-founded Social Chain before joining the BBC series Dragons' Den?

Steven Bartlett co-founded Social Chain before joining the BBC series Dragons' Den.

Social Chain is a social-media marketing agency and media company founded by Bartlett and Dominic McGregor. The pair established it in 2014, building a business focused on online communities, viral campaigns and digital communication. Bartlett’s career in social media made him notably different from Dragons whose backgrounds were rooted mainly in traditional retail, manufacturing or property.

Bartlett later became an investor on Dragons' Den, bringing experience from the digital economy and from building a prominent modern brand. His appointment reflected the programme’s continuing effort to include investors with expertise relevant to technology, social platforms and younger entrepreneurs.

Social Chain is not the same as Bartlett’s podcast or later personal-media projects. Those ventures expanded his public profile, but Social Chain is the company associated with his early entrepreneurial success and co-founder status. The founding year and co-founder are the key identifiers for this question.