Alistair Turner and Anthony Coates-Smith received £160,000 from investors Duncan Bannatyne and Richard Farleigh on the BBC2 programme.

Now their food transport business, Igloo Thermo Logistics, has been valued at £4 million and the pair have been tipped to eventually enter the Sunday Times Rich List.

Igloo operates 40 refrigerated vans that can deliver food or pharmaceuticals that need to be kept at a precise temperature. They are based in depots in Leeds and Watford and the firm’s clients include Marks and Spencer.

Mr Coates-Smith told the Telegraph that business had boomed since the Dragons’ Den appearance.

‘It sent our sales into orbit,’ he says. ‘We have doubled our capacity and we are still fully booked.’

Investor Duncan Bannatyne says: ‘The two lads were extremely believable. They had an existing business, a service business, which is the industry I work in. I was able to help them straight away.’