After the First World War the Royal Navy debated whether the compass platform should be enclosed to protect the command from weather. An entirely open bridge was ideal for night action, particularly since glass windows reflected the glow of instruments. However, it was far too drafty and it could be too wet. Considerable effort went into designing wind deflectors which would cause updrafts (or prevent downdrafts) and thus keep a bridge habitable. There was also the threat of strafing, which was re-emphasised by bombing trials against the ex-battleship Centurion (1933). Bridges had to be protected without ruining visibility. By 1933 the compass platforms in Royal Sovereign and Barham had been completely enclosed. Ramillies was being given similar treatment, except that the wings of her compass platform had no overhead protection. This arrangement was planned for Repulse and would probably be followed in Warspite, Malaya and Royal Oak (it was not). Charthouses, remote control houses and plotting offices were protected with bulletproof plating as ships came in for large repairs. However, a CO fighting his ship against air attack should be able to see the whole sky, for example to be able to order prompt evasive manoeuvres.6 The Royal Navy’s solution was to keep most of the compass platform open, but also to provide a protected shelter.
The Lion bridge structure became the prototype for other British battleship bridges up to the Queen Elizabeth class. This is Centurion, which was built with a simple pole foremast like that in Lion. Like Lion, she had a rangefinder in an armoured hood atop her conning tower. During the First World War the small armoured hood atop the conning tower (with a 9ft rangefinder on an Argo mounting inside the tower) was supplemented by a steel box carrying a 15ft rangefinder.
Once it was clear that a rangefinder should be mounted in the foretop, the foremast had to be stiffened. King George V shows the flanges initially used. The circular foretop housed a 9ft rangefinder. Later another such rangefinder was mounted on the compass platform. During the war the flanges were replaced by tripod legs.
The Royal Navy seems to have been unique in seeing an analogy between surface and anti-aircraft fire: in each case targets had to be chosen and designated to directors and to weapons. A Home Fleet air defence committee organised in the latter part of 1934 pointed out that although a modern battleship might be able to engage as many as six air targets at the same time, her CO would see little of the air situation from his roofed bridge. Air attack would develop suddenly. A dedicated Air Defence Officer (ADO) had to prioritise threats and keep the CO informed. He should be in direct contact with both the principal air lookouts and the CO. The proposed organisation was tested on board Nelson and Rodney. By mid-1936 the ADO idea had been accepted throughout the fleet. Ships under refit were being given suitable open bridges.7 Thus in 1936–7 Royal Sovereign and Resolution had air-defence positions occupied by six special lookouts. The ADO had a bearing/elevation transmitter with which he could designate observed targets to the two high-angle directors and also to the pom-poms. The CO or another officer could indicate a target to the ADO position using bearing and elevation transmitters on the compass platform. During the Second World War the ADO office expanded to include a gun direction room (GDR) fed largely by radar, an element of the Action Information Organisation (AIO). The abortive 1920 capital ships and the Nelsons introduced a new type of bridge, a slab-sided tower needed to support the heavy new director control tower (DCT) required for the new fire-control system (see below). In muchmodernised form, this type of bridge appeared both in the new battleships and in the four heavily-rebuilt ships.
The follow-on Iron Duke class had much the same bridge as the King George Vs, but it had a full tripod foremast and also a heavy steel casting atop its conning tower, carrying a 15ft rangefinder (a 9ft rangefinder was inside the conning tower). This is HMS Iron Duke at Constantinople (Istanbul) in 1920, part of an Allied force attempting to enforce the peace settlement with Turkey. She had a main-battery director above her foretop (which was used to control main-battery fire using spotters) in a coaming serving as a screen for lookout positions. A range dial is visible on the fore side of the coaming. One of the two secondary-battery directors is visible on a platform low down one of the legs of the foremast. The superstructure level above it (charthouse/searchlight platform) carried a 9ft rangefinder on each side (in the rest of the class the positions were reversed). The main battery was controlled (using spotting) from the foretop, below the coaming protecting the main-battery director. The structure visible above the compass platform was the ‘primary control position’. It carried a 9ft rangefinder for torpedo control on its roof (one of its arms is barely visible). The steel casting of the 9ft rangefinder is visible above the conning tower, just behind ‘B’ turret and the vertical object to the left is a semaphore. A 9ft rangefinder was carried inside the conning tower. The structure below the foretop was a 6in gun spotting position. The after superstructure carried a 2m (6.56ft) anti-aircraft rangefinder, neither visible here. Each turret also carried a rangefinder: 9ft (as built) in ‘B’ and ‘Q’ turrets, 25ft in ‘Q’ and ‘X’ turrets and 18ft in ‘Y’ turret.
HMS Queen Elizabeth is shown as Grand Fleet flagship in 1918, as photographed from USS New York. She has a main-battery director above her foretop, protected from splinters by a coaming. Inside it is a 12ft rangefinder. The platform immediately below the foretop is for torpedo lookouts. The shelter at the after end of the compass platform carries a 15ft rangefinder for torpedo control and probably also to support tactical plotting. Two 9ft rangefinders on the forebridge or elsewhere in the bridge structure supported the 6in torpedo defence guns. The lower part of the compass platform carried a pair of 6in directors (vertical cylinders, one of which is visible poking above the splinter mattress). The conning tower carried a 15ft rangefinder in a combined director/rangefinder steel casting. A second such rangefinder was aft, for torpedo control (atop the torpedo-control tower). The after superstructure also carried a 2m (6.56ft) high-angle rangefinder. All of the turrets carried 15ft rangefinders, but ships were refitted post-war with 30ft rangefinders for their high turrets, the ends of whose housings projected well beyond the sides of the turrets.
The Royal Sovereigns were conceived with dramatically stripped-down bridge structures. Royal Oak is shown as completed. Note that her main-battery director was mounted below her large oval spotting top (presumably shaped to accommodate a 9ft rangefinder), rather than above it, as was typical. She had 6in directors in the wings of her compass platform. There was no upper steering position; the only helm was inside the conning tower. Revenge and Royal Sovereign had this type of bridge. Resolution and Ramillies, the last to be completed, had something closer to earlier practice, suggesting dissatisfaction with the new type.
Beginning with the rebuilt Queen Elizabeths, the heavy conning tower was eliminated. The heavy-calibre hits it had been conceived to defeat would be relatively few at long range, but at night a ship might be peppered. Without control, she would be a danger in a melee. The tower bridge was therefore provided with a lightly-protected steering position, from which it was hoped the ship would normally be steered, whether or not in action. In Warspite the front and sides were 3in NC, the back 2in NC, the roof 1½in NC and the floor 1in NC. This was intended to resist shells and bombs bursting near the conning position, but not to protect against direct hits.8 After C-in-C Home Fleet visited the mock-up of Renown’s bridge at Portsmouth (and then the bridge actually installed on board Warspite) he wrote to DNC that these positions should be protected against close-range attack by destroyers or