This paper was first published in the Journal in 1947 (Vol. 1, p. 118). Sections 1 and 2 are summarized in order to save space. Sections 3, 4 and 5 are reprinted with only a little abridgment. The paper is followed by comment from the original author.

The original paper gave a comprehensive account of the development of navigational radar in the United Kingdom from the beginning of World War II up to the time of writing.

The use that was made of the very early radars was mentioned and the improvements brought about by the introduction of the PPI (Plan Position Indicator) and centimetric radar were described. An account was given of how radar assisted the Normandy landings, and of the techniques employed including the use of radar predictions of the Normandy coastline (produced in great secrecy) which were optically superimposed on the PPI. Also shown on the predictions were the planned approach tracks to the shore. An example of one of these predictions compared with the post-invasion radar photograph is shown in Fig. 1. This superimposition of geographical information on the PPI was to become of great significance in later years.