She was the last Royal Navy ironclad to be built which had a propeller that could be hoisted out of the water to reduce drag when she was under sail, and the first to have an armoured deck.

[2] This meant in particular the ten French armoured corvettes of the Alma and La Galissonnière classes,[3] though the ironclads of the smaller navies of Asia, and the Americas also featured.

At the same time as Shannon was being planned, the Imperial Russian Navy launched the first armoured cruisers, General-Admiral and her sister Gerzog Edinburgski.

These ships were intended for the traditional cruiser mission of commerce raiding, but were armoured and armed on the same scale as a second-class ironclad.

The existence of these ships meant that Shannon was now expected to act as a counter to them, and perform the commerce protection missions which had previously been the preserve of unarmoured cruisers, most recently the Inconstant.

[7] At the point the belt ended, a 9 in armoured bulkhead ran across the ship, the top of which formed the embrasures for the 10-inch guns on the upper deck.

She had three masts, and was initially given a ship rig with 24,000 square feet (2,200 m2) of sail, a point insisted on by the Director of Naval Operations, Captain Hood.

While she accomplished more than Swiftsure or Audacious on a more limited displacement, and was the equal of a foreign 'station ironclad', she turned out to be far too slow to be an effective cruiser.

While her heavy reliance on sailing efficiency was inevitable given her role, this was incompatible with the speed required to catch a foreign cruiser.