"Effingham" arrived at Portsmouth for the necessary repairs on 9 January 1940. Her engines had to be stripped down and her boiler tubes replaced; her "pom-poms" and their directors were finally installed during this time, as was her catapult. The ship was not ready for action again until 12 April when she sailed to Scapa Flow. The Navy intended "Effingham" to participate in Plan R 4, during which British forces would occupy Narvik, Norway, and the iron mines in Kiruna and Malmberget, Sweden if the Germans invaded Norway. The British plan had been rendered obsolete when the Germans invaded on 8 April.