Manchester became the main production base for Dragon's Den after the programme moved from London.
The British series was originally produced in London, but production later relocated to Manchester. The move formed part of a broader concentration of BBC production activity in the city, particularly around MediaCityUK in Salford Quays. That area became a major centre for television production and broadcasting.
The relocation did not change the programme's core premise. Entrepreneurs still enter the pitch room, present their businesses and negotiate with the investor panel. What changed was the production setting and the wider regional base supporting the series. The programme is therefore linked both with its earlier London studio history and with its later association with Greater Manchester.
Manchester and Salford are sometimes used interchangeably in descriptions of the production move, because MediaCityUK is in Salford within Greater Manchester. The canonical city answer used for the show's production base is Manchester. This is a location question, not a question about where entrepreneurs live or where their businesses operate.