We turned up on a miserable wet Sunday morning to meet Peter G, our guide for the tour - he called it "liquid sunshine". Well, he wasn't far wrong because we forgot the terrible weather as he guided us through the tour in a very entertaining and informative way. The stories he told were really interesting and the whole experience was very worthwhile - all for £6.
For those who wish to do further tours there is a £1 option at the end of the tour which means that you can do further tours for a reduced price, so that can't be bad.
Highly recommended - wear comfortable shoes and bring wetgear.