"It was during my second year at university that I possibly made my first contribution to the war effort. A large series of oblique air photographs had been taken of extensive kelp beds - probably off the north and west coasts of Scotland. What we geography students were asked to do was to calculate the areas of these beds. All we were given were the angles at which the photographs were taken and the height of the aeroplane above sea level.

We were given an intensive course on how to tackle the problem, none of which I can now remember. I know it involved complicated calculations for which the only assistance we had were books of 7 or 10 figure logarithms - no computers or even calculators in those days. However, eventually we were able to draw equal-area grids on the photographs and so estimate the total areas of kelp.

What the purpose of this exercise was we never discovered. Later investigation found that the ash produced by burning various kinds of seaweed had been an important source of potassium and iodine until early in the 19th century when recovery of these elements became unprofitable (except during WWI) as they were available from other sources much more cheaply. 22 tons of seaweed produced one ton of ash which contained 10-13% of potassium sulphate and 1-6% of iodine.

Of course, there might have been quite a different purpose bearing in mind the date, late 1942. Food supplies were getting short and nourishment derived from plentiful supplies of seaweed might have been very welcome. No significant amounts of weed are normally used for food in Europe - the only use I know of in this country is for laverbread production in West Wales - but in the Orient some seaweeds are used for food and in the making of soups and condiments, so the use of seaweed to bolster our dwindling food supplies might have been considered.

As our final exams approached the chief cartographer of the Hydrographic Department of the Admiralty now based in Bath, came to visit the geography department in Cambridge in search of desperately needed new recruits. The geography professor, Frank Debenham, had been approached by Admiral Sir John Edgell, the Hydrographer of the Navy with whom he had been acquainted since the time when they had both been involved in different ways in Scott's last Antarctic expedition.

The hydrographer was told that there were three possible recruits, students studying cartography and mathematical geography. So he sent his chief cartographer up to Cambridge to check us over. All three of us had informal interviews there and then and were later called for interview at the Admiralty itself in Whitehall where we were closely questioned by a rather terrifying panel which included two senior naval officers.

After a week or so we each received telegrams informing us that we had been appointed to posts in the Hydrographic Department and requesting that we report to Bath as soon as possible. I am afraid the arrival of a telegram gave my mother quite a shock as in wartime telegrams almost invariably meant bad news. We were very lucky to get these jobs as all single women and married women without children between 18 and 41 were either directed into work of national importance or had to join one of the women's services.

Accommodation in Bath at this time was very scarce. A large part of the city down by the river had been almost completely flattened in one of the so-called Baedeker raids. New recruits were billetted in a requisitionted boarding school, the pupils having been evacuated elsewhere. We were lucky to be allocated beds in a four-bedded room, probably an ex-classroom, as most people had to put up with dormitory accommodation.

For us this billet had one great advantage - it was only five minutes walk from the place where we were to work. In anticipation of the outbreak of hostilities the Admiralty had had built five blocks of hutments on top of Lansdown on the northern side of the Avon valley in Bath, to provide offices for staff that might need to be evacuated. There were four blocks on side of the road and one, the Hydrographic Department, on the other. Being a naval department it probably considered itself superior to the civilian departments on the other side of the road, and so might have merited special treatment!

The Hydrographic Department was under the direct control of the First Sea Lord with a naval officer, usually an admiral, in overall charge. It consisted of an oceanographic branch and chart branch. Chart branch was run by another naval officer known as Superintendent of Charts. It was to a subdivision of this known as CB2 that I was appointed.

Each section occupied half of one wing of the hutment block comprising a small office for the section chief, a larger one for the deputy chief and two cartographers and a large drawing office for the draughtsmen of two adjacent sections, Bout a dozen in all. A cartographer's job was defined as 'the calculation, compilation and correction of charts'. The draughtsmen produced fair copies ready for the printing works which were now in Taunton, having been removed from Cricklewood at the outbreak of war.

The first thing we were asked to do on reporting for duty was to read and sign the Official Secrets Act, so I hope nothing here will contravene that. More...