In the first years of the 20th century the M&GNJR was doing well financially. Long-distance expresses were run to the area from northern English cities as well as from London. Restaurant cars were put on, as well as workers' trains, for example bringing fish-processing women from northern Scotland for seasonal work. Fish had become an important traffic since the N&SJR connection to Lowestoft had been established. Although some short sections of double track had been introduced, the majority of the network was single line, and this brought challenges to timekeeping at busy times. The Midland and GNR were operating trains on the line as of right, and the GER had acquired running powers over several sections and to some terminal stations. Conversely the M&GNJR needed the cooperation of the GER for some penetrating workings, at a time when competition with the GER was still intense. In May 1906 the committee approved introduction of the Whitaker tablet exchange apparatus. On single-track sections, head-on collision due to signalman error was prevented by a token system: drivers of trains entering a single line section must be in possession of a physical token, a "tablet" specific to that section, and one only could only be released from control equipment in the one or other of the two signalboxes controlling entry to the section. When the train had passed through the section the tablet was placed in the apparatus at that end of the section, and only now another might be released either there or at the other end of the section. When non-stopping trains passed the tablet had to be passed from the signalman to the fireman of the train, and this could not be done at speed without injury. Whitaker devised a mechanical apparatus to be placed at the lineside and on locomotives to enable the exchange at a higher speed. During World War I many of the best long-distance express passenger trains were suspended; the M&GNJR took on considerable additional goods traffic during hostilities, and many of the workforce left for the armed forces. The company maintained an armoured train, constructed by the London and North Western Railway at Crewe, continuously in steam from early in 1915 in case of enemy invasion. After 1918, government control of the railways continued, and much traffic in demobilised servicemen tested the capacity of the network. There was a general railway strike in the latter months