The Devastation class was designed as an enlarged, ocean-going, version of the earlier Cerberus-class breastwork monitor.

[4] The ship carried a maximum of 1,800 long tons (1,829 t) of coal, enough to steam 4,700 nautical miles (8,700 km; 5,400 mi) at 10 knots (19 km/h; 12 mph).

Shortly after completion, Thunderer's forward turret's weapons were replaced by more powerful RML 12.5-inch (318 mm) guns.

The armoured citadel protected the bases of the gun turrets, the funnel uptakes and the crew's quarters.

[2] Thunderer, the fifth ship of her name to serve in the Royal Navy,[11] was laid down on 26 June 1869 at Pembroke Dockyard, Wales.

[12] Construction was subsequently halted for a time in 1871 to modify the ship to improve her stability and buoyancy by extending the breastwork to cover the full width of the hull which increased the ship's freeboard amidships and provided additional accommodation for the crew.

One of her boilers burst as she proceeded from Portsmouth Harbour to Stokes Bay to carry out a full-power trial.

[19] The ship suffered another serious accident on 2 January 1879,[20] when the left 12-inch 38 ton gun in the forward turret exploded during gunnery practice in the Sea of Marmora, killing 11 and injuring a further 35.

The men in the turret often stopped their ears, and perhaps their eyes, at the moment of firing, and then instantly worked the run-in levers, and did not notice how much the guns had recoiled.

Both guns were at once reloaded, and the rammer's indicator, working by machinery, set fast and failed to show how far the new charge had gone.

"[21] The accident contributed to the Royal Navy changing to breech-loading guns, which could be more conveniently worked from inside the turrets.

One piece of evidence supporting the double loading theory was the presence of an additional stud torn from a Palliser shell, found amongst the wreckage within the turret.

[26] The ship rejoined the Mediterranean Fleet in March 1891, but was forced to return home in September 1892 with persistent boiler problems and she was reduced to the Chatham reserve.

Thunderer became the guard ship at Pembroke Dock in May 1895 and remained there until she returned to the Chatham reserve in December 1900.

Rear-Admiral John Wilson, a former captain of the ship, stated in a meeting of the Royal United Services Institute discussing the most acceptable types of battleship in 1884,[17] "I also agree with my friend Captain Colomb that we have no type of ship to my fancy equal to the Dreadnought or the good old Thunderer.

Give me the Thunderer, the hull of the Thunderer; she had bad engines, she was not arranged as I would like inside, she was badly gunned as we all know, and she had not enough light gun or sufficient armaments; but she carried 1,750 long tons (1,780 t) of coal, could steam at 10 knots from here to the Cape, and could fight any ship of her class on the salt water.