Lord Roberts sets his sights on reaching Johannesburg before the Boers wreck the mines; Begbie’s Armaments Factory, which lies south of central Johannesburg, is turning out thousands of rounds of ammunition for the Boers.

The Boers suspect sabotage by Johannesburg’s uitlanders when an enormous explosion occurs at the factory and a swathe of land is flattened. In the meantime, the Boers, themselves, have adopted a guerrilla strategy, blowing up strategic bridges and railway lines, including the single line from the Cape ports to the Transvaal, along which Lord Roberts intends to advance to Johannesburg. British engineers quickly work out how to solve these hitches and when Roberts reaches Johannesburg in May 1900, the Boer commandoes flee in confusion. Roberts sets up his headquarters on a farm, Syferfontein, on the outskirts of town. When St Mary’s purchases part of Syferfontein in the 1930s, the wood-and-iron headquarters become part of school property.

The British government annexes the SAR and the Union Jack, already flying in Bloemfontein, is hoisted in Johannesburg as well.