Sub : life on board with the hidden heroes of the Royal Navy's silent service

At any given time, any number of the Royal Navy's 15 nuclear submarines lurk undetected in the world's oceans.

Totally self-sufficient for months at a time, they lie in readiness to be deployed to listen, intercept, or attack wherever they may be needed. And should the UK be devastated by a nuclear strike, they might just be the last military force standing.

Award-winning journalist Danny Danziger has been allowed unprecedented access to one of the attack class submarines of the 'silent service', joining the crew on operations for weeks on end, living among them and hearing their stories.

Unrestricted and uncompromising, it paints a vivid picture of this enigmatic branch of our armed forces.

In an increasingly unstable world, these are the people who are in the best position to keep us safe.

It is time for the silent service to be heard.