Mick O' Farrell was 25 and 5 months old when he enlisted on 12 August, 1915. He described hmself as a horse trainer and had already had marked success with his horse, Zephuron, who own the Grand National Steeple in 1914. He enlisted as Michael Farrell, though at least one of his brothers was still O'Farrell, as was his widowed mother. He was one of six children, three boys and three girls, of W. O'Farrell of Bendigo and his wife, Eileen. Mick O'Farrell also had a fiancee, Maude McGuire.

His love of horses and experience with them made it natural that he would be a driver. He was sent ot Albert Park for initial training and placed in the 4th Field Artillery Brigade, 10th Battery. The Brigade was only formed in September and consisted of three artillery batteries, the 10th. 11th and 12th Brigades. The 4th FAB left Melbourne for Suez on 18 November, 1915, on board HMAT 'Wiltshire' A18.  Once at Suez, the recruits joined the 2nd Division, already in camp and an older AIF unit. On 14 March, they moved to Alexandria and then left for France a week later, arriving at Marseilles on 19 March, 1916.

From Marseilles the 4th Brigade batteries were sent to the Somme, an 800 kilometre journey by rail, stopping at Le Havre to pick up 18 pounder guns and vehicles, before they went on to Armentieres, on the French border. Here Mick O'Farrell became the driver of a six horse team, bringing ammunition to the troops fighting at Pozieres.

The battle of Pozieres was one part of the larger battle of the Somme, designed to relieve pressure on the French troops at Verdun. The 4th Brigade was deployed south, at 'Sausage Valley', so called by the British troops, a shallow valley, south of the village of La Boisselle, and near Pozieres. It was by now late July and there was constant action against the Germans. Mick o'Farrel was driving his team up the valley with ammunition for the troops when he was wounded, hit by shrapnel from a shell. He was taken to the 3rd Casualty Clearing station , then to hospital in Rouen, where he died three days later.

Bomber Pardy, 6391, gave evidence of what happened:

I knew Farrell well; he was a race horse owner in Australia. He was a driver in the artillery and was inaction in Sausage Gully when a whiz-bang burst among his team, killing two horses and wounding three. Farrell was badly wounded and died some days later. Driver Howe was also wounded and is now in Blighty. Bevan was not otuched and got the M.M. for bringing the team out. I was with him when he was decorated. It was he who told me all about it.

Bombardier William Harold, 6715, also made a statement:

I am nearly certain that Bombardier Farrell was killed by the premature explosion of a gun behind his battery. One of our own guns behind fired and the shell burst as soon as it left the muzzle. The guns were so close together that he was killed.

It would seem, then, that Mick Farrell died as the result of an accident, the misfiring of one of the allied eighteen pounders. He was buried at Puchervillers British Military Cemetery, Puchervillers, Somme, France, on the AWM 145 Roll of Honour Cards and on Panel 13 in the Commemorative Area of the Australian War Memorial, Canberra.

An article in a local Frankston paper recorded his death:

PATRIOTIC.   Driver M. J. O'Farrell, a good  sport, and well known in Frankston, was wounded in action in France, and died of his injuries on 31st July. He was known in sporting circles as Mr Farrell, and owned and trained Zephuron when he won the V.R.C. Grand National Steeplechase in 1914. Driver O'Farrell was the youngest son of Mrs E. O'Farrell, 96 Powlett street, East Melbourne, and the late Edward O'Farrell, formerly of White Hills, Bendigo At one time he was a popular footballer in Bendigo He was also a cricketer and good rifle shot. Two of his brothers are serving abroad.

His family placed a death notice in 1916 an In Memorium notice in The Argus in 1917:

O'Farrell: In loving memory of our dear brother, Michael James, (Mick), 6th Battery F.A.R., died of wounds receieved at Pozieres, July 31, 1918.

                                                   They laid our hero down to rest

                                                   In a flag with a Southern Cross

                                                  And we mourn him as one of the best

                                                  For his death is Australia's loss