Iron Duke Class Part I


HMS Iron Duke at Weymouth Bay 1927 by Randall Wilson. (P)

Iron Duke, a veteran of the Battle of Jutland and Flagship of Lord Jellicoe at that engagement, is seen here painted in the rays of the setting sun at Weymouth Bay 1927.


HMS Iron Duke at the Battle of Jutland’


The original design was for a modified King George V 21-knot battleship with four broadside torpedo tubes and no stern tube.

Five layouts were submitted to the Admiralty by the DNC Phillip Watts, all featuring a main armoured belt of 12in thickness and running for 360 feet of the hull. Although following the lines of King George V in general – including main armament, a distinctive retrograde step was seen in the sketch proposal which featured a reverse in the mast/funnel arrangement as in the earlier Orion class of 1909 (see sketch). During preparation, however, the disadvantages were forcibly pointed out and the idea was not pursued any further. Of the five layouts (see table) M1V was approved and funds were allocated for four of the type without question, a war with Germany seeming very likely and sooner rather than later.

Enlarged dimensions over the King George Vs and Iron Duke (so named later during construction) represented the ultimate development of the basic Orion type from which the design was evolved through the intervening KGVs. They were the first British dreadnought type with a 6in secondary battery and the first to be given any type of anti-aircraft guns.

As completed they were nominally 2,000 tons heavier than King George V with increases of 25–26 feet overall in length, 1 foot in beam and 6 inches on the designed draught. The marked rise in displacement was necessitated by the heavier and better protected secondary armament, augmented torpedo armament and slightly increased fuel capacity. There was a design called ‘MV’ which was the same as ‘MIV’ but with an armoured belt reduced to 8in and 7in, but it does not appear to have been given any further consideration.

The additional length in this class was allocated over the forecastle and quarterdeck, in the former case to provide some buoyancy against the weight of the 6in battery and set it back from the bows, and in the latter to accommodate the two main deck 6in guns aft. The freeboard was considerably lower than in many of the previous British dreadnoughts and, in fact, was not equalled until the arrival of the Royal Sovereign class in 1913. The main armament layout was practically identical with that of King George V but with director control in all of the class as completed.

The 6in gun had last appeared in the King Edward VII class (1906–7), but as an auxiliary to the main armament rather than for anti-torpedo purposes for which 12pdrs and 3pdrs were provided and, in conformity with the ideas of the First Sea Lord (Admiral Fisher), none of the intervening classes had carried anything heavier than a 4in anti-torpedo armament despite repeated criticism of its ineffectiveness against contemporary destroyers.

As shown in the tables one of the original designs had featured a 4in secondary armament, but a report prepared by Admiral Mark Kerr in 1909 suggesting the change and noting the majority of service opinion favoured the 6in gun for any torpedo work as well as general use against heavy ships during close-range action, made the 6in battery almost the principal feature of the design.


Full tripod foremast close before fore funnel.

Tall topmast stepped abaft control top.

Short topgallantmast stepped before, except in Emperor of India which completed with short flagpole only.

Heavy forward strut at starfish below control top.

No mainmast as completed.

W/T aerials carried direct to the stern or after superstructure.

Tall derrick stump for main derrick fitted close behind second funnel. Very short stumps abeam this (P&S).

Long derrick slung from each forward corner of after superstructure. These could be topped up vertically or crossed against forward face of superstructure.

The rig was very similar to that of King George V except that this class were completed with full tripod foremast. They were the last battleships built for the Royal Navy with the distinctive single masted rig which had been a feature of the three preceding classes.


Considered not such good-looking ships as King George V mainly because of the small round funnels. Sternwalk fitted in all except Emperor of India.

Distinguishable from King George V by:

1. Forecastle battery and 6in gun on each side of main deck aft.

2. Small round equal-sized funnels.

3. Full-length tripod legs (KGV similar from 1917).

Individual differences (as completed):

Iron Duke: Small rangefinder over bridge.

Marlborough: No rangefinder over bridge (1914 only).

Benbow: Shallow triangular strut to derrick stump.

Emperor of India: No sternwalk; no strut to main derrick stump (added 1915–16).

After the Naval Treaty of 1930 it was concluded that the Iron Duke class would be scrapped with the exception of Iron Duke herself which would be demilitarized and put to use as a Gunnery Training Ship. The relevant clause in the treaty stated that Iron Duke was to be refitted as soon as possible, in fact the work was to be commenced within twelve months of ratification of the treaty and had to be completed within eighteen months. A great deal of thought was given to her demilitarization and the question arose as to what smaller guns could replace the 13.5in which were to be removed.

Twin 8in were very much favoured at the time, but these would involve a great deal of rearrangement of the barbettes and supports, so 6in and 4.7in were fitted, but some experimental fittings were tested throughout the thirties with an eye to refitting other battleships with a suitable secondary armament when their time came for reconstruction. A total of 4,258 tons was removed


Displacement (tons): 26,300 (load), 31,620 (deep) (average for class).

Length: 580ft 4in (pp), 623ft 9in (oa) (average for class).

Beam: 90ft 1in.

Draught: 28ft 10in (load), 32ft 6in (deep).


10 × 13.5in 45cal Mk V, 12 × 6in Mk VII, 4 × 3pdr 5 × MG, 2 × 3in AA, 4 × 21 in (submerged).


Main belt: l2–9–8in, bulkheads: 6–4in, upper side bulkheads: 8in, barbettes: 10–9–8–4–3in, turrets: 11–5½–4in, CT: 11–6–3in, decks: forecastle 1 in; upper 2–1¼in, main 1½in, middle 2½in-1in, lower 2½, magazine screens 1½in.

Searchlights: 8 × 36in, 2 × 24in signalling. Improved control arrangement fitted.


Runways on 13.5in turret tops (‘B’ and ‘Q’). Emperor of India fitted for towing kite (balloons). During post-war period aircraft not normally carried, but embarked when required for exercises.


Parsons direct-drive turbines driving 4 propellers.

Boilers: 18 Yarrow (Babcock & Wilcox in ID and Benbow).

SHP: 29,000 for 21 knots.

Radius of action: 8,100 nm at 12 knots.

Fuel (tons): 900 coal normal load, 1,050 oil, 3,250 coal max. Max. speed slightly less than 20 knots due to extra weights added.

Rig: Short topmast and no topgallant. Very long forward strut at starfish in Emperor of Indio and Iron Duke. Twin W/T spreaders on after superstructure (short in Emperor of India, tall in other three).


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