The largest number of messages ever registered in Hut 8 on one day was on March 13, 1945 when 2133 were registered.
As a general rule German Naval traffic was sent out in 4 letter groups with the indicator groups at the beginning and repeated at the end. Both from the German and our own point of view this made Naval traffic easily recognizable and gave a check on the correct interception of the indicator groups. Messages were normally broadcast and on fixed frequencies which changed comparatively rarely, so that it was possible for the cryptographer without W/T knowledge to keep the different frequencies and the areas to which they belonged in his head. The principal exception to this were the U Boats which used a complicated W/T programme, but from our point of view identification of services was made easy by the use of an independent set of serial numbers for each service. We should have had some difficulty also with the Mediterranean area if the intercept stations had not given a group letter to each W/T service and appended it to the frequency when teleprinting the traffic.
Except for a short period in the early days of Bonito, fixed call signs were always used though it was unfortunately by no means always possible to tell from whom a message originated. "Addressee" call signs - a very great help to the cryptographer - were little used except in the Mediterranean where, if we were fortunate, it might be possible to tell both the originator and the destination of a message. Like the Mediterranean keys, Bonito gave a lot away by its call signs but other keys stuck to the old procedure. The only exception of any note to this rule were the emergency W/T links which replaced teleprinter communications if the latter broke down.
From early days Scarborough was our chief intercept station and was responsible for picking up most of the traffic. Other stations were brought in if interception at Scarborough was unsatisfactory, as was often the case in the Mediterranean and North Norwegian areas. For a considerable time North Norwegian traffic was being sent back from Murmansk while the W/T station at Alexandria played an important part in covering many Mediterranean frequencies. The principal disadvantage of traffic from distant intercept stations was the length of time it took to reach us. Traffic came from Alexandria by cable and an average delay of 6 hours between time of interception and time of receipt at B/P was considered good.
Unlike Hut 6 we never controlled the disposition of the various receiving sets at our disposal but made our requests, which were considerable, through Naval Section. As I do not ever recollect an urgent request having been refused, this system worked very satisfactorily from our point of view.
The reason for our numerous demands for double, treble, and