This bundle of letters (1899-1900) covers the period just before and during Mark's involvement in the South African War (1899-1902). They are interesting from a war experience perspective, as they document his activities as part of the militia, and provide conversations overheard from the men, attitudes and opinions of his contemporaries, and his opinions on the war, its administration, its causes and the possible outcomes. His time in South Africa was mainly characterised by boredom, low morale and complete inactivity. The incompetence of army leadership and the constant unfulfilled promise of being relieved by army regulars are frequently mentioned. The letters give the impression that a supposedly great Empire's army should have been no match for a makeshift collection of Dutch peasant farmers, but were frequently outsmarted and out-manoeuvred by their guerrilla tactics (considered dishonourable) and knowledge of their own terrain. Mark frequently voiced his expectations to be returning home within a few months, and yet did not return to England until after the war ended in 1902. This shows the complete inability to measure any progress of a war fought on unfamiliar territory according different combat rules. Opinions on key military and political figures of the day, such as Kitchener and Cecil Rhodes, also provide interesting reading.

On a personal level, these letters give us an insight into his relationship with both Edith, and his parents. Throughout the course of these letters, there was the financial problem of his mother's excessive debts, which not only delayed his departure to South Africa, but continued to occupy him during his time at war. After the settlement of Jessica's creditors had been arranged, further unacknowledged debts came to light, causing more damage to Mark's already diminished allowance. She was also instrumental in spreading rumours in England of his marriage to Edith, and Edith's travel to South Africa to hasten the match. Though it was Mark's intention to marry Edith, these bully tactics and money motivations did not coerce him into something he would only do once he was prepared in his own time.

His relationship with Edith also develops through the letters. The first four letters are appropriately addressed to Miss Gorst, and signed Mark Sykes, a convention which then changes to the more affectionate address of Honourable and well beloved co-religionist, signed from the Terrible Turk (or T.T.) Mark Sykes. The letters often show Edith's insecurities, as Mark frequently reassured her he had not found anyone else, and that she had good qualities that he admired in her, such as sincerity and honesty. There was also continuing banter about spelling mistakes, on both sides, and a strange fascination with butterscotch!