Fewer than half the successful pitches on BBC hit show Dragons’ Den ever saw a penny of investment, new research has found.

In an analysis of all 143 businesses that successfully won cash on the show between series 1 and 11, just £5.8m of the £13m pledged was ever invested.

The study was conduced by Tiger Mobiles, a smartphone comparison site, which unsuccessfully applied to appear on the show in 2008.

The deals fall apart after the show due to several reasons, Dragons’ Den investor Deborah Meaden told the Telegraph. “I’ve had entrepreneurs with extremely unfortunate health issues, patent issues, and two or three silences where I never hear from them again.”

Issues frequently arise during due diligence, she added. “I spent £5,000 to £10,000 on each company and sometime things aren’t what they seem.”

Many entrepreneurs appear on the show primarily to gain publicity for their business. When sales surge following the airing of their episode, they pull out because investment is no longer necessary.

“The world explodes for them after Dragons’ Den,” Ms Meaden said. “They get offered better deals in some cases, or think they don’t need the Dragons. But what they find when the publicity dies down is that they still need help running the business.”