During May the Battalion was inspected by Col. S. H. Godman, D.S.O., commanding the Division, who presented C. S. M. Risley, D.C.M., with his medal. The Battalion also received a visit from Lieut.-Col. E. T. Rodney Wilde, V.D. At the end of May the Division was reviewed by Field-Marshal Earl French, commanding the Home Forces.

Although the whole of the Battalions at Hurdcott and Fovant Camps existed for the training of recruits and were in no way formations which were likely to be sent overseas as units, they were included in the scheme which had been prepared for the defence of Great Britain in the event of an attempt at landing by the Germans.

This scheme provided for the maintenance of a permanent defence force on the East Coast and at other points where it was deemed likely that any attempt at invasion would be put into effect. In addition to this, arrangements were made for the rapid concentration from other sources of a mobile force for use, in the event of active operations taking place, as a general reserve. To this general reserve the units of the 3rd line groups of the 1st London Division contributed a quota of officers, N.C.O.'s and men varying from time to time with the numbers of men who were sufficiently advanced in their course of training to render their inclusion in the force useful.

During the period at Hurdcott frequent test concentrations took place, in several instances the parade being followed by a test route march. These parades were always attended by the platoons of the 4th (Reserve) Battalion detailed for the time being to this duty and passed off satisfactorily.

On the 2nd June 1916 Major W. H. Hamilton, who had commanded the Battalion since its formation, was gazetted to the 4th Battalion Duke of Cornwall's Light Infantry and almost immediately proceeded to join his new Battalion at Meerut.[4] He was succeeded in temporary command of the Battalion by Major G. H. M. Vine. On the occasion of Major Hamilton's departure the troops testified to their appreciation of his unfailing kindness and sympathy with all ranks throughout the period of his command by lining the camp road and heartily cheering him as his car passed down it.

[4] Major Hamilton remained with the 4th D.C.L.I. until the following year when he was attached to the 4th Hants Regiment. With this Battalion he proceeded to Mesopotamia and took part in the victorious advance which culminated in the occupation of Baghdad. He was later appointed to command the detachment of the Hants Regiment which accompanied the gallant little force led by General Dunsterville to endeavour to secure the oilfield of Baku on the Caspian Sea.

In the latter part of July command of the Battalion was assumed by Col. Vickers Dunfee, Major Vine resuming the duties of second in command.

On the 1st July 1916 began the great series of battles on the Somme, the Regiment's part in which will be described, and almost immediately calls were made for drafts of all ranks to fill the very serious gaps caused by the heavy casualties sustained by the 1/4th Battalion during the battle of Gommecourt; and between this date and the middle of October when the 56th Division was finally withdrawn from the Somme battles a total of some 30 officers and 400 other ranks were despatched. These very heavy calls naturally depleted the ranks of the home Battalion very seriously and took nearly all the "Derby" recruits who had joined in the previous March.

With the object, apparently, of effecting an ultimate economy in staff, a reorganisation of considerable importance took place on the 1st September 1916 among the whole of the 3rd line units of the Division. So far as the Fusilier Brigade was concerned this took the form of amalgamation of the four existing battalions into two, the 1st and 2nd Battalions becoming the 1st (Reserve) Battalion, and the 3rd and 4th Battalions becoming the 3rd (Reserve) Battalion. Each of these new battalions for the time being retained a double establishment of officers, warrant officers and N.C.O.'s and were organised in eight companies till the despatch of personnel on draft permitted a reduction to be made. The composite battalion was made responsible for the provision of reinforcements and for the reception of ranks returned from overseas for each of the two Regiments of which it was composed.

These amalgamations of necessity involved extensive repostings of officers, in particular among those of senior rank. Command of the new 3rd (Reserve) Battalion was assumed by Lieut.-Col. T. Montgomerie Webb, formerly commanding the old 3rd (Reserve) Battalion, Major G. H. M. Vine being appointed second in command. The duties of Adjutant, Quartermaster and Training Officer respectively were also assumed by officers of the old 3rd (Reserve) Battalion (namely, Capt. McGlashan, Capt. Coombe and Major H. Moore, M.C.), the officers who had previously held the corresponding appointments in the old 4th (Reserve) Battalion being posted as follows:—