I have cropped the cap and collar badges from the photo's on Brett's web-site and believe the crux of the matter is in the shape of the flames above the bomb.
I refer to the book "Military Badges of the British Empire 1914 - 1918" by Reginald H.W. Cox.
(1) I do not believe these men have anything to do with the H.A.C. as the H.A.C. cap badge was similar to the other artillery badges - namely the field gun, but with HAC on a "ribbon" above the gun carriage wheel and under the crown. They did have exploding bomb collar badges, but the shape of the flame was long and narrow and pointed at the top - a bit like the shape of a poplar tree.
(2) Similarly, I do not believe that they have anything to do with the Grenadier Guards. According to RHWC's book, GG's did wear the bomb badge, but the flames were VERY rounded across to top and protruded almost twice the width of the bomb itself - the flames were very "flat" looking.
(3) Because of the shape of the flames on your photo's, I believe the main contender has to be one of either the 1st, 2nd, 3rd or 4th (City of London) Battalions Royal Fusiliers. After the 4th Battalion, the design was quite different. Having cropped your photo's and blown them up, (no pun intended!) all but one badge on your men had triangular shaped flames coming out of the bomb - a bit like the spade shape of spades of playing cards. I could find no other references to "spade" shaped flames in the book - only to these four battalions of the R.F's. Officer's badges were bronze - O.R's badges were gilding metal.
Sunday, 2 March 2008
Identification of regiment from military uniforms (4)
The following analysis of the badges and uniform was made by George Cogswell, who comes to a somewhat different conclusion: