The Prince Consort class of ironclad battleship were four Royal Navy wooden-hulled broadside ironclads: HMS Royal Oak, HMS Prince Consort, HMS Ocean, and HMS Caledonia. They were originally laid down as , but were converted to ironclads. Royal Oak was Britain's fifth ironclad battleship completed.
Prince Consort, Ocean, and Caledonia were built to a common design and are today known as the Prince Consort class, though contemporaries knew them as the Caledonia class. Royal Oak was their half-sister.
Genesis
The of nine 91-gun two-decker steam line-of-battle ships were laid down between March 1859 and October 1860 (a further three were ordered, but never laid down, and eventually cancelled in 1863). Their dimensions were the same as (101 guns), but had a new timbering plan to suit the smaller armament. The reduction in armament was intended to improve the efficiency of the guns. Bulwark and Robust were suspended in March 1861 in an advanced state of construction and were eventually broken up in March 1873 and August 1872 respectively. The remaining seven ships of the Bulwark class were less complete state and were converted into 'ironclad frigates'. Of these Triumph (later renamed Prince Consort), Ocean, and Caledonia were converted to 'broadside ironclads' with 1,000 nhp engines. Royal Oak had a similar conversion but with the original 800 nhp engine. Royal Alfred, Zealous and Repulse were later converted into 'central battery ships'.
Reasons for the conversion programme
When the first British ironclads were conceived, the Surveyor (Rear Admiral Sir Baldwin Wake Walker) said, "They must be regarded as an addition to our force, as a balance to those of France, and not as calculated to supersede any existing class of ship; indeed no prudent man would, at present, consider it safe to risk up the performance of ships of this novel character, the naval Supremacy of Great Britain." For this reason, the Royal Navy continued to lay down and complete steam two-deckers and three-deckers. However, in 1861, it was clear that Britain was falling behind in ironclads laid down (see table below). The ten French ironclads laid down in 1861 were the start of the French programme of 1860, which was intended over a number of years to produce: 20 sea-going ironclads for the active fleet, 10 sea-going ironclads for the reserve fleet, and 11 floating batteries.
The British response to the French programme was taken in a number of steps.
On 28 September 1860, the Board of Admiralty decided to order three new iron-hulled ironclads: one large - Achilles, and two medium-size - Hector and Valiant. Though there was still great uncertainty as to the value of ironclads, and the Controller was directed to report as to their "fitness for use as transports or other duties in case it should be deemed advisable at any time to strip off their armour plates."
On 7 February 1861 Rear Admiral Sir Baldwin Wake Walker resigned as Controller. He was replaced by Rear Admiral Sir Robert Spencer Robinson.
Following a report from the British naval attaché in Paris regarding the progress of the French 1860 programme, the Naval members of the Board asked for the provision of ten new sea-going ironclads and the adaptation of ten or more existing steam line of battleships for armour protection with a total outlay of £3,000,000.
The Prime Minister, Lord Palmerston, advocated cutting down and armouring the last sailing battleships rather than reducing the number of steam line of battleships. (In 1861, the fleet of steam line of battleships were extremely modern, and comprised the main battle strength of the Royal Navy.)
The Chancellor of the Exchequer, William Ewart Gladstone, had decided in November 1859 that ironclads must be the vessels of the future. In early 1861, he was willing to accept a bigger appropriation for armoured ships if it could be offset by reduction in expenditure on wooden line of battleships. Gladstone suggested that the navy build wooden-hulled ironclads like the French.
In March 1861, construction of the Bulwark-class two-decker steam line of battleships was suspended. Then in May 1861 it was decided to convert the five least complete ships of the Bulwark class into ironclads. It was also decided to lay down three new very large iron-hulled ironclads, which became the Minotaur, Agincourt, and Northumberland.