Drake, Royal William and RNH (presumably Royal Naval Hospital) are all satellite PABXs of Naval Base (Devonport). Information from dial labels at Anchor Surplus, Nottingham, during the 1990s. Drake is in fact Royal Navy barracks.
Defiant may be an alter ego of Federal (the letters equate to the same numerical code, 333) or it may be the exchange for HMS Defiant, a fleet accommodation and maintenance depot at Devonport.
Tennyson was a large Admiralty exchange in Bath, so large that it had its own name as if it were a public exchange. The following statement, by Monty Ellis, has the agreement and approval of the District General Manager, Bristol, given that the subject may even yet be considered to come within the provisions of the Official Secrets Act. Not, Monty imagines, that the information could be of any possible use to Her Majesty's enemies, because the Admiralty's system of PMBXs was superseded by PABXs in (he believes) the 1960s, and in any event, the Ministry of Defence has entries for all its establishments at Bath, plain for all to see, on p.104 of the current directory!
I believe the following information about Tennyson "exchange" to be correct, although the evacuation of part of the Admiralty staff from London to Bath took place in 1941, whereas I did not take up duty in Bristol T.M.O. until I was demobilised in 1947.
It must be remembered that security was at stake, but it did not matter if the enemy found out that the Admiralty was served by Tennyson exchange, so long as it was concealed from him where it was physically situated. Had the Admiralty establishments been small enough, it seems to me that it would have been quite acceptable to serve their PMBXs by groups of ordinary exchange lines from the Bath auto exchange, provided that it was kept secret that Tennyson and Bath were one and the same exchange. However, I have no doubt that the volume of trunk traffic alone to and from the PBXs was far in excess of the capacity of the auto plant at the time. For this reason, the Tennyson PBXs were served in my time by direct groups of circuits, which in effect were Trunk Sub lines, to and from the Bath Trunk Exchange.
According to the Post Office Circular (P.O.C.), Tennyson opened on or about 19th February 1941. Since Bath Trunk Exchange did not open until 16th September 1944, and prior to that Bath was no more than a minor exchange in the Bristol group, it appears highly probable that Tennyson was served initially by Trunk Sub circuits from Bristol Trunk, although I have been unable to obtain confirmation that this was so.
Tennyson consisted of four principal PBXs—
Foxhill .............. approx 18 CB1 positions
Ensleigh ............. 10-12 CB1 positions
Warminster Road ...... approx six PMBX1A positions
Empire Hotel ......... three PMBX1A positions.
—and there were one or two smaller PBXs which came and went as the accommodation situation altered, such as Pulteney Hotel.
I understand that the CB1 positions came from L/Maryland exchange [in east London]. The original operating staff came down from London, and consisted of the Admiralty's own personnel, but the costs were later made part of the Head Postmaster, Bath's establishment, and the Admiralty paid the Post Office for the hire of their services.
Tennyson undoubtedly appeared in the Exchange Routing File and, where the amount of traffic justified an entry, in visible index files (VIFs). The routings would have been first to Bristol, and later to Bath, as GSC. The controlling operator knew the routing, but the caller did not.
It follows from the above that Tennyson is very unlikely to have appeared in any local code dialling instructions. At the time in question, the UAXs may have had multi-metering up to 4th. fee (15 miles), and the subs. provided with Dialling Code Lists. But the ND exchanges did not have multi-metering, and although there was dialling-out to exchanges within unit fee range, the number of these exchanges was so small that the Dialling Instructions could be contained in the preface to the directory. The main point is, that if a code for Tennyson had been published, it would have given away the fact that the establishment must be within 15 miles (in the case of a UAX) or 5 miles (in the case of Bath itself). There may, however, have been small groups of exchange lines to the PBXs from Bath auto, but they would only have been used by people already "in the know".
The distinctive numbering ranges of the Tennyson PBXs were as follows—
Foxhill 0*** [generic number, Tennyson 0101]
Ensleigh 1*** [generic number Tennyson 1000]
Empire Hotel 6*** [generic numbr Tennyson 6100]
Warminster Road 8*** [generic number Tennyson 8600].
There were PW [private wire] routes between the PBXs, and from Foxhill to London and a number of other Admiralty establishments. To begin with, the operating staff were under the general charge of a supervisor who came down from London, a Miss Dashwood.
Trafalgar and Victoria
According to one Admiralty file at the PRO, Trafalgar and Victoria (naval, not public) exchanges were housed in or under the Admiralty Citadel. One of these, probably Trafalgar, was previously located during World War II beneath Trafalgar Square, with exits to street level opposite Canada House and in Charing Cross Road near the Tate Gallery; there are photographs of the manual switchroom in the Imperial War Museum. Another report states that the exchange equipment was in tube-type tunnels, close to Trafalgar Square, running off the main Whitehall tunnel system and that photographs exist in the BT Archives. The two reports are not mutually exclusive.
In this way this exchange (Trafalgar) was connected to the deep level tunnels, as were telephone facilities located underground where the Queen Elizabeth Conference Centre now stands in Victoria Street (presumably the original Victoria admiralty exchange). Another deep-level exchange during WW2 was that of the US forces in the Goodge Street tunnel complex.
See also Army and GTN tp dirs.