One of the winners of business finance from the Dragons' Den television programme has taken to the streets to find angel investors after his offer from the show fell through.

Umbrolly, which was offered £150,000 in the first episode of the first series of the programme, said today that it had launched a week-long mobile billboard advertising campaign in the City to raise finance to launch its Mini Wall-Mounted Umbrella Vending Machines.

Managing director Charles Ejogo said that the company had found it difficult to raise finance from City institutions. He added that he was hoping to raise between £100,000 and £300,000 from the public to build and install the vending machines in railway stations, shopping centres, bars, and office buildings across the country.

This sum was too large to raise from friends and family, he said, but too small to be of interest to banks or venture capitalists.

"Our adverts are as much a last attempt to find investment for our own business, which will otherwise collapse, but also an attempt to highlight the lack of options available to small high growth businesses seeking investment in the UK today," he said.

"The general public have always backed our business ever since it appeared on Dragons' Den, and with investments as little as £10,000 being accepted, we hope that they will see this as a great opportunity to invest in a unique business."

Vans displaying 6 metre-by-3 metre advertisements would be placed outside the square mile's Tube stations from 7am until 8pm every day this week, Umbrolly said, to catch the attention of passers-by.

The BBC said that the deal with Umbrolly stalled, "...when Charles couldn't install machines on the Tube as he promised in his pitch."

Daniel Ronen, chief executive of business advisers DoS UK, said that it was common for such investment arrangements to fall through and that start-up companies should not count on promised investments until they had a signature on paper and the funds were transferred.

"It's very common to have just a heads-up agreement, but you have to read the small print. Deals collapse all the time, continuously - even sometimes after you have the signature. The golden rule is, whoever has the gold makes the rules," he said.

However he was optimistic about Mr Ejogo's approach to his problem.

"This guy feels that people have pulled out, but he's not giving up and is really living his entrepreneurial vision. He's doing what it takes. Someone's going to like the guy for the balls he's got, for the drive he's got. He's saying, 'Fine, I'll get the money from someone else'."