Movies might have us believe that bomb disposal comes down to cutting the right wire. In fact, explosive devices are complex and varied - and learning how to dispose of them safely involves intense training, as well as the ability to stay calm under pressure. This was the world of Dr Gareth Collett, a retired British Army Brigadier General and engineer, specialising in bomb disposal; whose 32-year military career took him around the world, including heading up major ordnance clearance projects in Iraq and Afghanistan. After retiring from the army, Gareth became a university lecturer – but following his diagnosis with bladder cancer, started researching a possible link between bomb disposal veterans and higher rates of urological cancers. In conversation with Professor Jim Al-Khalili, Gareth discusses this ongoing research, dealing with PTSD - and why he just can't watch Oscar-winning movie The Hurt Locker...