If you've not seen the prior three episodes in his four parter, this spin off casts an analytical eye over the highs and lows experienced by the hundreds of entrepreneurs who have braved the Den over the last nine series, packed with tips and advice so that even the least entrepreneurial amongst us can benefit from the advice. This week, the Dragons share their thoughts about how the strength of an idea is the key to unlocking their cash in the Den. Back in 2007, eccentric inventor Mark Champkins was looking for investment in his range of school products and ended up giving Peter Jones 40 percent of all his future ideas. But has the entrepreneur delivered on the Dragon's investment? Cousins Lisa Marshall and Shelene Mitchell were two of the most unlikely entrepreneurs the Den has seen, but they surprised the Dragons with a water-tight patent for their stackable outdoor plant container. And when Hairdresser Shaun Pulfrey demonstrated his hair-detangling brush... Someone who could do with a brush is Rab C Nesbitt... he's only after getting a new series (10.00pm, BBC2) after not long enough, And this one guest stars Richard E Grant.