'Solo I' was a British deception plan to support 'Torch' by persuading the Germans that the Allies were about to make landings at Narvik and/or and Trondheim on the west coast of German-occupied Norway (1 August/November 1942).

Schemed and implemented by the London Controlling Centre in tandem with 'Overthrow', 'Solo I' was designed to persuade the Germans to retain as great a military strength as possible in Norway as possible, and was in effect a reiteration of 'Hardboiled' based on the 'story' that landings, this time in the areas of Trondheim and Narvik, were to be undertaken from Scotland at a time early in November. Double agents were used to report public speculation that Norway was about to be invaded and to pass on supposed accounts of major military activity in Ayrshire, special commando training, the stockpiling of tyre chains and engine coolant anti-freeze, and that Swedish co-operation was being sought. Rumours were also spread in Stockholm that the British were training special pioneer companies of Canadian lumberjacks, and that the US Army was scouring its personnel for men who spoke one or more of the Scandinavian languages.

A major radio simulation programme of substantial movements of warplanes to Lossiemouth and Kinloss, the obvious Scottish air bases for a Norwegian campaign, began late in October, as too did intense anti-submarine and aerial reconnaissance activity over the North Sea. Specimen billeting and requisition forms were printed, 20,000 Norge shoulder flashes were ordered, arctic kits and maps of Norway were issued, troops were lectured about the nature and dangers of frost bite, and rumours were spread about the imminent issue of woollen underwear and special wind-proofed jackets. The Americans were asked to circulate a report that Lascar merchant seamen, whose contracts limited their service to latitudes below 60° N, were being offered bonuses to serve in the colder climates of latitudes above this. Practice exercises in landing against a rocky coast were undertaken. When the departure of the fictional expedition was scheduled, 14 US merchant ships assembled for a convoy to Murmansk in the northern USSR were used to made a dummy run as far north as the Orkney islands group.

Like 'Overthrow', 'Solo I' had as one of its primary advantages the fact that it played directly on Adolf Hitler’s permanent concern about Norway as 'the zone of destiny of this war', as he told Grossadmiral Erich Raeder in March 1942, and therefore the UK’s inevitable intent to attempt the country’s recapture. On 26 August, Raeder referred to 'the constant threat of an enemy invasion' as a reason for keeping strong naval forces in northern Norway. Late in September reports were received that the Germans foresaw an invasion by 10 divisions which, it said, were being concentrated in the Orkney islands group. On 19 October, Hitler ordered the reinforcement of Narvik and the improvement of the defences to this port. On 2 November, central and northern Norway were placed on full alert. As the nights of the winter months lengthened, Hitler became ever more fearful that the Allies would exploit the longer hours of darkness for a surprise descent on northern Norway and, as late as 22 December, worried that January would be the most dangerous month for Norway. Given these and other factors, it is hardly surprising that in 1942 no German ground forces were withdrawn from Norway for service elsewhere.