'Mespot' was the Allied overall designation for the cover and deception policy for the whole of North-West Europe up to 21 days after 'Overlord', and as such the precursor to 'Fortitude' (January 1944).

The basic Allied deception policy established in 'Bodyguard' was what came to be known as the 'postponement' or 'delay' concept to suggest to the Germans that the Allies could not attempt any amphibious assault over the English Channel until the late summer of 1944 at the earliest and then, if and when the Germans came to realise that a cross-Channel operation was in fact imminent, 'the tactical cover plan prepared by Supreme Commander, Allied Expeditionary Force will come into force with a view to deceiving the enemy as to the timing, direction and weight of "Overlord".' The notional start date for this 'tactical cover plan' was to be chosen by General Dwight D. Eisenhower, in his capacity as the supreme commander, but the 'Bodyguard' concept made a strong recommendation that the date be later than the the 'Overlord' D-Day 'with a view to delaying the dispatch of enemy reinforcements for as long as possible'. This 'postponement' theme dominated the minds of the deception planners for some and was then simply abandoned.

The Combined Chiefs-of-Staff Supreme Allied Commander team has initially concentrated its efforts on the 'Appendix Y' (originally 'Torrent') cover and deception plan for the 'Neptune' (iii) first-day assault on Normandy. This was an uninspired undertaking intended to persuade the Germans that the assault would be made from south-east England onto the coast of the Pas de Calais, and was based on an attempt to make it seem that there were larger forces in south-east England than there really were. This was to be achieved, it was hoped, through the agency of 'discreet displays' (poor camouflage) of false camps and weapon dumps, etc, and then, on the assumption that the Germans would see that an invasion was imminent when the troops moved to preparatory positions and were loaded on the invasion craft, 'creating' a force of six divisions in south-east England for a fortnight after D-Day. It was assumed though never actually specified that the GHQ Home Forces would play the role of this force.

Right through January 1944 there were meetings to develop a new and more convincing plan for the supposed Pas de Calais threat and also for a threat to Scandinavia, and to the pair of these target areas the codename 'Mespot' was allocated. A first draft of the deception planners' concept was issued for comment on 3 January; an initial meeting was held on 7 January; an improved draft was circulated on 11 January, there was a senior planners' meeting on 14 January; and on 17 January a definitive draft was circulated with the first details of a plan which was to use false activity in the south-east of England and other places to persuade the Germans that the preparations they would be allowed to 'observe' during the spring were associated with a large-scale invasion of the Pas de Calais top be launched in the middle of July (D+45). Thus the Germans, it was hoped, would be taken by surprise when the real landing came six weeks earlier than they had been led to believe, and in Normandy and the Pas de Calais.

The 'Mespot' proposal paid little attention to the situation after the launch of 'Overlord' in Normandy, suggesting only the creation of a 'story' that six divisions were being assembled in south-eastern England to carry out a subsidiary operation in the Pas de Calais 'with the object of drawing German forces away from the main target area'.

As such, 'Mespot' was little more than a slightly improved 'Appendix Y', and garnered little more approval than its predecessor. Two British generals, neither of them even directly involved in deception, immediately noticed one of the main problems with the 'delay' theme: if the Germans were able to observe Allied preparations sufficiently to judge their state of readiness, the real activity in southern and south-western England would lead them to expect an invasion on or about 1 June, while pointing false activity in south-eastern England toward 15 July would mean that they might not notice anything at all in that region until after the launch of 'Overlord'. Even if the Germans did evaluate what they saw as suggesting 1 June in one place and 15 July in the other, they might 'split the difference', or come to the conclusion that Normandy was to be invaded on 1 June and that something would then happen in the Pas de Calais six weeks later, providing them with the time to deal with the situation in Normandy before turning to any possible situation in the Pas de Calais.

Colonel D. I. Strangeways, one of the ablest British deception planners, was quick to appreciate these problems, and even before the meeting of 14 January had become so concerned that he threatened to terminate any association with the matter and started to agitate for an altogether superior scheme, for which he gathered influential support and which began to take shape as 'Fortitude'.