Here’s a unique sight to thrill all submariners.

Nope, not clear skies over Barrow, but the very first dive of the Silent Service’s newest state-of-the-art leviathan: HMS Ambush. The second of seven Astute-class boats made her maiden dive in a huge basin at BAE Systems’ yard in Cumbria, ten months after she was officially unveiled to the world. The hunter-killer was moved from her berth to an enormous 25-metre-deep (82ft) ‘dive hole’ long enough and wide enough to accommodate her – and almost deep enough to completely submerge the submarine.