After the affair at the spruit De Wet again dispersed his burghers, with orders to hold themselves in readiness to muster at short notice.  He had not long to wait before he saw another opportunity of employing them.

A small force, less than 1,000 strong, was covering, half-way between Harrismith and Bethlehem, the construction of the main blockhouse line to Kroonstad, under the personal superintendence of Rundle.  The force was broken up into three detachments, which were too far apart to render each other effective support in case of a sudden attack.

The strongest detachment, consisting, however, entirely of Yeomanry, was posted on Groen Kop, three miles distant from Rundle’s Head Quarters.  The position is fairly strong, and resembles a wedge lying on the veld, with a gentle ascent from the east to a plateau to which the normal level rises steeply on three sides.  A mile or two to the S.E. it is commanded by a higher eminence, from which a party of Boers had already been expelled.  It was not, however, occupied, and De Wet promptly made use of it as an observation post, for which it was admirably adapted, as it looks down into the British position on Groen Kop.  Moreover, the customary movements for protection, such as the relief of outposts, were carried out with such extraordinary laxity and neglect that De Wet was soon able to acquaint himself with almost every detail of the defence.  Even the emplacements of a field gun and a pom-pom were disclosed by shots casually fired for range-finding purposes.

On Christmas Eve De Wet saw that he had before him a prey that would fall into his hands as easily as Sannah’s Post or Waterval Drift, and he resolved to clutch it at once.  His burghers, though dispersed, were within call, and a force of over 1,000 was quickly assembled.  With unerring instinct he selected the steep N.W. corner of the Groen Kop wedge as the point of attack, reasoning that the defenders would think themselves adequately protected in that direction by the nature of the ground.  On Christmas morning, soon after midnight, over 1,000 Boers were in position under the broad end of the wedge.  They were not discovered, as no patrols had been sent to watch the ground beneath, and the sentries on the crest gave no sign.

The pioneers of the storming party attained the crest at 2 a.m.; and not until then was the alarm given to the dormant camp.  The position, after a struggle which lasted but an hour and a quarter, was captured by De Wet, who, ere the midsummer sun had risen, was hurrying away with British prisoners of war, guns and wagons, which neglect of the ordinary precautions by a body of unprofessional troops had delivered into his hands.

At Rundle’s Head Quarters, only three miles away, the sound of the firing had attracted attention, and a weak body of Mounted Infantry, the only mounted force at his disposal, was sent out to see what was the matter.  It was unable to intervene with effect, and returned to report the situation.