Grand Designs - Season 20 Episode 4 -

Kevin McCloud follows the progress of engineer Richard Bennett and his partner Felicia Böhm as they transform an underground water reservoir near the Humber Estuary into a family home. In 2013, the pair decided to embark on the ambitious build with a budget of only £150,000, but it proved a monumental challenge, and design and layout decisions stretched their abilities and the schedule to the max.