Look up at the giant frigate propeller

No photo quite prepares you for the experience of seeing this huge screw propeller from a type-23 frigate looming over your head.

If you had to pick one object that makes the modern Royal Navy go, this massive propeller would have to be the one. Standing underneath it, you enjoy a view that few land-based creatures will ever get.

This bronze-alloy propeller was made for a Type-23 frigate, the core warship of the Royal Navy's surface fleet.

Type-23s were originally designed to patrol the North Atlantic on the prowl for submarines. The propeller is specially designed to minimise underwater noise and prevent detection by enemy submarines. Combined with an innovative propulsion system, two low-speed propellers like this give the Type-23 frigate its reputation as an ultra-quiet anti-submarine ship.

There are currently 13 Type-23s in active service in the Royal Navy, making up half of the frigate/destroyer force.

Powerful and versatile, these 133-metre (436 ft) ships take part in a wide range of tasks including surveillance, anti-piracy operations and disaster-relief work.

They are often called 'Duke-class' frigates as they are all named after British dukes. Type-23s were built at the shipyards of Swan Hunter (Tyneside) and Yarrow's (Glasgow).