The officer commanding was an engineer, Lt. Chard. The main body of troops were infantry.
I am not qualified to make a serious assessment of the British outfits involved but I do remember thinking it was a combination of Engineers and Infantry along with some Boer scouts.
I am not sure how accurate the movie was but it showed a group of Engineers working before the attack.
Bromhead was the other subaltern. I didn’t know the Royal Army at that time used infantry troops to do engineering details.