Inside Turkish hunter-killer sub TCG Birinci İnönü as its crew take on key Nato training role

Turkey's TCG Birinci İnönü is a Gur-class hunter-killer submarine powered by diesel-electric engines, capable of diving to 300 metres and staying submerged for around 50 days. 

Rosie Laydon took a tour of the sub and saw how its crew of 40 live and work in tight conditions, with sailors rotating bunks in a system known as "hot bed". 

Lieutenant Commander Orkun Turan explained how the submarine can act as both a hostile target and a training partner, helping Nato forces sharpen their anti-submarine warfare skills. 

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The Executive Officer says the boat is built to challenge surface ships, maritime patrol aircraft and helicopters, with the one classic submarine guiding principle: staying silent and undetected.