Five years ago revolution erupted in Libya as rebels rose up against the rule of Colonel Muammar Gaddafi. A bloody civil war followed and Gaddafi was captured and killed in October 2011. The golden gun he was carrying was displayed by his killers as a trophy of their triumph. Today, Libya remains divided and violent, with so-called Islamic state becoming stronger there every day. Gabriel Gatehouse returns to Libya to find those who seized Gaddafi's golden gun, and report on IS's rise. Contains distressing images from the start.