And it was high time, as the next day :
The Times, Wednesday, January 17th, 1900
"YORKSHIRE.- The first Yorkshire detachment of the Imperial Yeomanry has now been completed. It consists of two companies of 240 men of all ranks, who are now stationed at Sheffield Barracks. The task ofmaking the final selection was a difficult one in consequence of the number of volunteers. Yorkshire, however, is not to be represented by one detachment only, and when the two companies now training quit the barracks the men whose offers in the first instance have had to be refused will be called upon to form a second detachment. The following officers have been recommended to the War Office for service with the two companies : -Yorkshire Dragoons.-Captain Crichton-Browne, Captain Simpson, Lieutenant Smith, Lieutenant Jeffcock, and Lieutenant Doxat. Yorkshire Hussars.- Major Gascoigne, Lieutenant Wombell, Lieutenant Beresford-Peirse, Lieutenant Wilson, and Lieutenant Mackillop. Captain Crichton-Browne is an officer of the Militia battalion of the King's Own Scottish Borderers, and has served for three years in South Africa in the Rhodesia Horse. Major Gascoigne served in the Nile expedition, 1884-85, as an officer in the Royal Horse Guards".

You will have noted that the Yorkshire detachment was (a bit prematurely !) announced as "forming the 13th Brigade" ; the Imperial Yeomanry was eventually rather organized in Battalions, the Yorkshire Hussars forming the No.9 Company of the 3rd Battalion.

The departure for South Africa would not wait for long, and on Sunday, January 29th, in Liverpool (Langton Dock), "Companies No.9, 10, 11 and 12, a total of 578 men , with 457 horses, arrived at the Alexandra  Dock Station, Liverpool, and embarked on board the Winefredian (transport 78), of the Leyland Line. No.9 Company, the Yorkshire Hussars, numbered 122 rank and file, under Captain Trench Gascoyne, and Lieutenants McKillop, Beresford-Peirse and Wilson."

Lieutenant Bereford-Peirse's status would again change soon :
"War office, Pall-Mall, February 2, 1900.
THE IMPERIAL YEOMANRY
To be Adjutants.-(...) Lieut. H.B. de la P. Beresford-Peirse, Yorkshire Hussars, with the temporary rank of Captain in the Army."

Some more official paperwork was to come along - one really gets the feel that the whole Imperial Yeomanry scheme was a kind of administrative nightmare to the War Office clerks :
"War office, Pall-Mall, February 9, 1900.
MEMORANDUM
The undermentioned Officers are seconded for service with the Imperial Yeomanry :-
Yorkshire Hussars (Princess of Wales's Own). Lieut. H.B. de la P. Beresford-Peirse."

The Yorkshire Hussars (or rather, No.9 Company) landed in South Africa on the 20th February.
They were one of the lucky Companies to have come along with a full complement of their own horses - remount was to be problematic for other units.
The Yeomanry Companies were directed on arrival in Cape Town to the nearby Imperial Yeomanry camp at Maitland, where they completed their training and waited for the other Companies to reach South Africa.

The 3rd battalion was under the orders of Lieutenant-Colonel G.I.Younghusband. They were part of the contingent sent in March to Mafeking, attached to Lord Methuen's Column. They engaged the enemy at Boshof in April :
"from The Great Boer War, by Sir Arthur Conan Doyle.
"In this short period of depression there came one gleam of light from the west. This was the capture of a commando of sixty Boers, or rather of sixty foreigners fighting for the Boers, and the death of the gallant Frenchman, De Villebois-Mareuil, who appears to have had the ambition of playing Lafayette in South Africa to Kruger's Washington. From the time that Kimberley had been reoccupied the British had been accumulating their force there so as to make a strong movement which should coincide with that of Roberts from Bloemfontein. Hunter's Division from Natal was being moved round to Kimberley, and Methuen already commanded a considerable body of troops, which included a number of the newly arrived Imperial Yeomanry. With these Methuen pacified the surrounding country, and extended his outposts to Barkly West on the one side, to Boshof on the other, and to Warrenton upon the Vaal River in the centre. On April 4th news reached Boshof that a Boer commando had been seen some ten miles to the east of the town, and a force, consisting of Yeomanry, Kimberley Light Horse, and half of Butcher's veteran 4th battery, was sent to attack them. They were found to have taken up their position upon a kopje which, contrary to all Boer custom, had no other kopjes to support it. French generalship was certainly not so astute as Boer cunning. The kopje was instantly surrounded, and the small force upon the summit being without artillery in the face of our guns found itself in exactly the same position which our men had been in twenty-four hours before at Reddersberg. Again was shown the advantage which the mounted rifleman has over the cavalry, for the Yeomanry and Light Horsemen left their horses and ascended the hill with the bayonet. In three hours all was over and the Boers had laid down their arms. Villebois was shot with seven of his companions, and there were nearly sixty prisoners. It speaks well for the skirmishing of the Yeomanry and the way in which they were handled by Lord Chesham that though they worked their way up the hill under fire they only lost four killed and a few wounded. The affair was a small one, but it was complete, and it came at a time when a success was very welcome. One bustling week had seen the expensive victory of Karee, the disasters of Sanna's Post and Reddersberg, and the successful skirmish of Boshof. Another chapter must be devoted to the movement towards the south of the Boer forces and the dispositions which Lord Roberts made to meet it."

The events would not always turn out so favourably, and the Morning leader would publish, on June 4, 1900 :
"Poor Yorkshire Hussars.
Writing home from the Convalescent Home, School of Mines, Kimberley, Private Jesse Helliwell, of the Imperial Yeomanry, says : « The poor Yorkshire Hussars are now not more than half theirstrength, there are s many sick and wounded and a lot of prisoners. I was lying in the ambulance during the engagement at Swarzkopjefontein, but I couldsee them peppering away. The Boers fired a few shells at us, but they could not get the range. It ias a terrible thing to see the dead and dying,but you get used to it. I think the Yorkshire Hussars have seen as much service as any, considering the time they have been here. »"

Here is an overall account of the services of the Yorkshire Yeomanry during the War (from "His Majesty's Territorial Army", by Walter Richards) :
"Few, if any, Yeomanry contingents did more brilliant work than did these Companies of Yorkshire Dragoons and Hussars. They were the first of the Imperial Yeomanry to reach South Africa ; and at Tweefontein, when that gallant soldier of fortune, de Villebois Mareuil, met his death, they took part in the first action in which the Yeomanry was engaged.They fought under Methuen and Hunter, under Milne and Ridley and Clements, Paget, Baden Powell, Hickman, and Plumer, Lord Erroll, Colonel Doran, and Colonel Scobell. From the 24th March 1900 to the 4th April 1901 the regiment was in action on thirty-nine occasions, fifteen of which were general engagements. Total miles marched 3173. The 66th Company took part in thirteen general actions, besides several minor engagements." The " new " squadrons compiled a record of almost constant fighting and wearisome "trekking ». It may well be wished that a regimental history of the achievements of the Yorkshire Dragoons and Hussars in South Africa might be published : it would be a valuable and inspiriting contribution to the annals of the War. In these pages it can only be attempted to mention— and that almost at random—a few of the occurrences in which they most signally distinguished themselves. At Rooidam in May we read in The Time’s History of the War that « The Yorshire Dragoons, at a gallop, seized a kraal from which a short advance enabled them to occupy a kopje enfilading the main position ; we hear of the Yorkshire Hussars distinguishing themselves themselves— and losing heavily—in a rearguard action with Olliver ; we hear of constant and severe fighting with the indomitable de Wet, of fierce conflicts at Lilydale, Jacobsdal, Hartbeetsfontein, and Senekal. Perhaps – for space forbids any approach to a detailed account—the most brilliant feat of arms to be recorded of the Yorkshire Yeomanry was that at Middlepost in February 1902, when " Lieutenants Chichester and Tabor were sent up to hold a ridge with the men of the Yorkshire Dragoons, their orders being that it was to be held till death. And held it was – till death. Both officers and five men were killed, and five men wounded. « They fought till the last man was down, it never entering into the head of any of these men to leave his post in any other way than on a stretcher. Of the many fine things done by Yorkshiremen at the front none should rank higher in the annals of the county than the way this little band of men lay on that stony kopje and quietly fought it out till there was none left to fight."

We can roughly follow Beresford-Peirse's steps in South-Africa thanks to his being awarded the Queen's South Africa Medal with four Clasps, "Cape Colony", "Orange Free State", "Transvaal" and "South Africa 1901", these Clasps being the ones usually observed on the Medals for No.9 Company.
They were awarded according to specific rules :
- Cape Colony : Awarded to troops serving in Cape Colony between 11 October 1899 and 31 May 1902
- Orange Free State : Awarded to troops serving in Orange River Colony any time from 28 February 1900 to 21 May 1902
- Transvaal : Awarded to those troops serving the Transvaal at any time between 24 May 1900 and 31 May 1902, who received no other clasp for action in the Transvaal
- South Africa 1901 : Awarded to those not eligible for the King's Medal although they had served at the front between 01 January and 31 December 1901 (to be eligible for the King's Medal, one had to serve in South Africa on or after 1st January 1902).

Beresford-Peirse was promoted to Temporary Major and Second-in-Command on June 1st 1900.
The term of engagement of Officers and men of the Imperial Yeomanry was for "one year, or not less than the period of the war".
The first contingent of the Yorkshire Hussars made their way home on board the Mongolian, leaving Cape Town on May 8th, 1901.
Major Beresford-Peirse was aboard, as well as "51 men of 9th Company" - to be compared with the 122 that had left for South-Africa the previous year.

There followed for Beresford-Peirse a few administrative operations :
"London Gazette, July 5th 1901
MEMORANDUM.
The undermentioned Supernumerary Officers are borne as absorbed into the Establishments of their respective units :-
IMPERIAL YEOMANRY.
Yorkshire Hussars (Princess of Wales's Own).-Lieut. H.B.de la P.Beresford-Peirse."

"War Office, Pall-Mall, 9th July, 1901.
THE IMPERIAL YEOMANRY.
The undermentioned Officers relinquish their commissions. Dated 10th July, 1901 :-Temporary Maj. H.B.de la P.Beresford-Peirse, second in Command."

Beresford-Peirse was mentioned in Earl Roberts's September 10th Despatch.
He was awarded a D.S.O. on September 27th, at the recommendation of Colonel Sir G.J. Younghusband :
"Henry Bernard de la Poer Beresford-Peirse, Major, 3rd Battalion Imperial Yeomanry.  In recognition of services during the operations in South Africa".
It would appear that he was actually mentioned twice in despatches during the War.
He was conferred his Order by King Edward VII at the Investiture held at St.James's Palace on December 17th, 1901.

It was not over with administrative operations yet :
"War Office, Pall-Mall, Jan. 3 1902.
THE IMPERIAL YEOMANRY (IN SOUTH AFRICA)
The undermentioned Officers, on having relinquished their commissions, are granted honorary rank in the Army as follows, with permission towear the uniform of the Corps :-
3rd Battalion.-(...) To be Hon. Majors : (...) Maj.H.B.de la Beresford-Peirse, D.S.O."

"War Office, March 4 1902.
MEMORANDUM
IMPERIAL YEOMANRY.
The undermentioned Officers resign their commissions and receive new commissions subject to the provisions of the Militia and Yeomanry Act, 1901, each retaining his present rank and seniority, viz.:-
(...) Yorkshire Hussars (Princess of Wales's Own). (...) Lieut.H.B.de la P.Beresford-Peirse, D.S.O."

A couple weeks later, on Friday, March 14th, he attended "a service (...) held (...) at Manfield Church, near Darlington, in memory of Colonel J.G.Wilson, C.B., of Cliffe-hall, who was killed at Klip Drift. (...) The lych-gates at the entrance to the churchyard were erected last June by public suscription in memory of Colonel Wilson's son, who also died in South Africa".
The latter, Lieutenant Richard Bassett Wilson, had died at Rustenburg on July 26th, 1900, of wounds received in action five days previously at Oliphant’s Nek - he was an officer of the Yorkshire Hussars.

It is to be noted that an unofficial tribute medal was awarded by the "Committee of the Yorkshire Volunteer Equiptment & Emergency Fund" to all members of the 3rd battalion (Yorkshire) Imperial Yeomanry "in recognition of their patriotism and the good service rendered by them in South Africa".

Beresford-Peirse would put his military career to an end the following year :
"War Office, 23rd January, 1903.
IMPERIAL YEOMANRY.
Yorkshire Hussars (Princess of Wales's. Own), Lieutenant (Honorary Major in the Army.) H. B. de la P. Beresford-Peirse, D.S.O., resigns his Commission. Dated 24th January, 1903."

Beresford-Peirse married on July 7th, 1904, Lady Mabel Marjorie Campbell, second daughter of the 3rd Earl of Cawdor (1876-1966). They had two sons, Henry Campbell (1905-1972) and Peter (1907-1984).
He became Clerk to the Wye fishery Board and Secretary to the Wye Fisheries Association, 1903-12. He was appointed Under Treaseurer, Middle Temple, 1912-30. He held the office of Justice of the Peace (J.P.) for North Riding, Yorkshire.
He succeeded to the title of 4th Baronet Beresford, of Bagnall, co. Waterford at the death of his father, on July 8th, 1926.
He died on May 14th, 1949.

Many thanks to Dave Knight, Stuart W. Elliott, QSAMike and Terry "Greenfield"