This is a bit of an old thread, but in the interest of adding more to the tale.
161 Brigade RFA was a "Pals" Unit, raised by local communities rather than by the War Office. The other 18 pounder batteries were from York, mainly Rountree employees. The three 18 pounder batteries would be joined by a 4.5 inch howitzer battery raised from Yorkshire miners.
We know quite a bit about 161 Brigade on the First Day of the Somme because the Brigade commander, Lieutenant Colonel A S Cotton wrote about it in the 1930s as "Reflections and recollections" R A Journal volume LXIII No 4. By and large the artillery barrage on the First Day of the Somme gets a bad press. This was the day when nearly 60,000 British troops become casualties, just under 20,000 fatally. But the 161st Brigade, reinforced by other artillery batteries supported the 97th Infantry Brigade in one of the few successful attacks in the northern half of the British Line, capturing the Leipzig redoubt south of Thiepval.
There were two reasons for their success.
1. The Infantry brigade commander had been an observer to the Russo Japanese war. He had noted that the infantry needed to be very close to the artillery barrage to succeed. This his highlanders crawled withion 50 yards of the German trenches before the barrage lifted.
2. One of either Colonel Cotton or the infantry Brigade commander noticed that the Germans were counter attacking and artillery fire was brought back from then barrage which had moved on.