Rhenoster River

The battalion's march was uneventful but, because there were scattered parties of Boers still active in the area, it had to deploy advance and flank guards at all times. It crossed the Vaal on 1 June and was about 15 miles (24 km) from Johannesburg when news arrived that the Boers under Christiaan de Wet had overrun several garrisons along the railway and destroyed the Rhenoster bridge. Roberts sent his chief of staff, Major-General Lord Kitchener back to organise the defence of the line of communications. Kitchener moved south with a column including 42nd and 44th Companies IY and brought the Boers to action near the Rhenoster river. 42nd Company was involved in two-hour fight to clear De Wet from his position, then early next morning the company was roused from its camp to ride 2 miles (3.2 km) to where the Boers were attacking an engineers' train. Later that morning they drove the Boers off some hills, but had to return to the camp which had been attacked. The following day (11 June) the two companies together with some infantry and artillery were ordered to escort a convoy of provisions to Maj-Gen Hector MacDonald's column at Heilbron. All went well on the first day of the march, but early on the second the convoy came under Boer shellfire and had to retire until the escort had cleared the Boers and the march could continue.^{[15][16][17][lower-alpha 1]}

Brandwater Basin

Imperial Yeomanry galloping over a plain during the Second Boer War.

By now 42nd Company had suffered a number of wounded and prisoners, and had had about 30 men evacuated sick (including Capt Gilliat), consequently it had been reduced to a fighting strength of about 70, commanded by Lt G.R. Smith-Bosanquet. The company joined Lieutenant-General Lord Methuen's column, which was cooperating with Kitchener's, and together they drove De Wet south-west towards the Brandwater Basin. A large force was now assembled under Lt-Gen Sir Archibald Hunter at Frankfort. This was joined on 29 June by MacDonald's column from Heilbron, including 42nd and 44th Companies IY and mounted troops from various units as well as the infantry of his Highland Brigade. 42nd Company joined Brig-Gen C.P. Ridley's 2nd Mounted Infantry Brigade. Hunter now took over all operations in NE Free State. Pushing De Wet into the Brandwater Basin he reached Reitz on 7 July and Bethlehem on 11 July. Here he established a base and disposed his forces in a cordon round the basin.^{[18][19][20][21]}

Hunter's drive through the Wittenbergen range into the Brandwater Basin began on 15 July, but that night De Wet broke through the cordon with some 2600 Boers, including President Steyn and the government of the OFS. The 4000 remaining Boers trapped in the basin surrendered on 30 July, but in the meantime Hunter sent his mounted troops, including Ridley's brigade, in pursuit of De Wet. This began the 'Great de Wet Hunt' as the Boer force zigzagged across northern OFS and southern Transvaal for the next two months. Ridley's brigade followed all the way. At the end of July Capt Gilliat disobeyed orders and rejoined 42nd Company. Trapped against the Vaal, De Wet broke through the British cordon once more. Kitchener then redeployed the columns to trap him against the Magaliesberg mountains, but again, De Wet broke through at Olifant's Nek. Ridley's brigade was then part of a force sent to relieve a British detachment that was surrounded at the Elands River. In mid-August 42nd Company marched via Rustenburg to Pretoria, where it halted to rest and refit. The company was depleted in numbers through sickness, and several officers had been posted to other duties, including Lt Sir George Arthur, who had been sent to the remount depot, and was able to supply the 42nd with good replacement horses.^{[22][23][24][25]}

Operations from Krugersdorp

A yeoman standing by his horse in South Africa

At the end of August 42nd Company was sent by rail to join Maj-Gen Fitzroy Hart's column at Krugersdorp. This force was based on 5th Irish Brigade together with artillery and IY (38th (High Wycombe), 42nd and 44th Companies). Leaving Krugersdorp on 30 August, Hart marched through northwestwards across the Mooi River, then on 9 September made a dash southwestwards for Potchefstroom with his mounted troops and some Irish infantry carried in mule wagons. The plan was to surround the town and make a surprise attack after dark. 42nd Company had furthest to go, a 30 miles (48 km) ride to get behind the town, but although the move was successful most of the fighting Boers had already left and joined De Wet. After a few days at Potchefstroom, Hart was ordered back to Krugersdorp, arriving on 30 September after a round trip of 300 miles (480 km).^[26]

At Krugersdorp the staff of 12th Battalion were dispersed – never having a full battalion to command – and Capt Gilliat became Officer Commanding Mounted Troops for Hart's Column. The column spent the next three months marching backwards and forwards, often at night, in an attempt to dominate its assigned area of 6–700 square miles. 42nd Company usually acted as flank guard or close escort to the artillery or the administrative 'tail'. Early in December Hart sent the 42nd and 44th Companies, with a detachment of the South Wales Borderers, to hold Orange Grove, but they were recalled to Krugersdorp in anticipation of an attack by Koos de la Rey on 16 December. The garrison dug perimeter defences and 'stood to', but the attack never materialised. The two yeomanry companies then rested at Krugersdorp and received a new issue of kit to replace their ragged clothes.^[27]

Richard Simkin's painting of an Imperial Yeoman.

At the end of January six men of 42nd Company forming part of a convoy escort were involved in an action at Modderfontein. The convoy was attacked at a pass in the Gatrand mountains on 25 January, but the yeomanry rearguard was able to hold off the attackers while the South Wales Borderers manned the pass and saw the convoy safely to Modderfontein. Next day the town was surrounded by Boers under Jan Smuts and subjected to intense fire. Lieutenant George Dymoke Green of 59th (Oxfordshire) Company, IY, (formerly a trooper in 42nd Company) volunteered to take party to hold a dominating kopje. The party, including the Hertfordshire men, held out for two days. Lieutenant Green was killed, but all six men of 42nd Company survived to be taken prisoner: they were released after 12 hours.^[28][29][30]

In early February Capt Gilliat was returning to Krugersdorp by train from leave in Durban. Outside Graylingstadt, near Heidelberg, the train was stopped by a mine and attacked by a party of Boers. Many of the officers aboard having left the train earlier, Gilliat was the only officer present, and he had only seven armed men from assorted units. They kept up a spirited defence while their ammunition lasted, losing two killed and two wounded, together with two civilian passengers killed. Gilliat was negotiating a safe conduct for the civilians and the Boers were looting the train when they were driven off by shellfire as a relieving force arrived. Gilliat resumed his position as OC Mounted Troops at Krudersdorp, and over the next two months he and his men patrolled the local area. At one point Hart's column carried out a setpiece attack on the Lossberg. Gilliat and his four squadrons galloped round the left flank of the objective, without coming under fire, only to discover that the Boers had already left on the approach of another British column of which Hart had been unaware.^[30]