Never heard of the Inns of Court Regiment before, but thanks to the magic of Google I found what seems to be a reliable history.
The modern history of the Regiment begins in 1859 with the formation of the 23rd Middlesex (Inns of Court) Rifle Volunteer Corps; it became the 14th Middlesex in 1889. The Regiment was attached, in its later years, to the Rifle Brigade and also formed part of the 2nd London Volunteer Brigade and the “Grey Brigade”. In 1888 a mounted infantry detachment was formed and became known as “B” (M.I.) Company. A contingent of 30 mounted infantry, 19 cyclists and 1 signaller joined the City Imperial Volunteers for service in South Africa during the Boer War. In 1908 the Territorial Force was formed and the Regiment became a Territorial unit, the 27th Battalion of the County of London Regiment (Inns of Court), but almost immediately it was changed into an officer training unit under the designation Inns of Court Officers Training Corps. The Regiment had an establishment of one squadron of cavalry (I.C.O.T.C. Squadron, formerly “B” (M.I.) Company) and three companies of infantry. In 1914 the Inns of Court Reserve Corps was formed consisting of former members of the Inns of Court Rifle Volunteers, and in 1917 the 1st Cadet Battalion, Inns of Court, was formed to train boys under military age.
In 1920 the Regiment was reformed with an establishment of one squadron of cavalry and two companies of infantry and in 1932 its designation was changed to the Inns of Court Regiment. The two infantry companies were converted to light tank cavalry squadrons in 1937 and two years later formed the Royal Armoured Corps Wing, Sandhurst. In 1939 the mounted squadron joined a cavalry training regiment in Edinburgh, but was disbanded in 1940. Between 1940 and 1943 the Regiment was the Armoured Car Unit of the 9th Armoured Division and from 1943 it was under the direct command of 1 Corps, the assault formation of 21 Army Group and later led the advance of 11th Armoured Division. On 1 April 1947 the Regiment was again reformed, as the Armoured Car Regiment of the 56th (London) Armoured Division, T.A., later to become the Reconnaissance Regiment of the 54th East Anglian Division. In 1956 the Northamptonshire Yeomanry was reduced to one squadron and amalgamated with the Inns of Court Regiment as “the Northamptonshire Yeomanry “D” Squadron, the Inns of Court Regiment”; and in 1961 a further amalgamation occurred when the Regiment and the City of London Yeomanry (Rough Riders) united under the title “Inns of Court and City Yeomanry”.
The “Rough Riders” had been formed in 1901 as the 1st County of London (Rough Riders) Imperial Yeomanry, but its name was changed to the City of London (Rough Riders) Imperial Yeomanry in 1902. Thereafter the Regiment’s name changed to City of London Yeomanry (Rough Riders), then City of London Yeomanry Battery, R.H.A. and 11th (City of London Yeomanry) Light Anti-Aircraft Regiment, R.A. before reverting to City of London Yeomanry (Rough Riders) prior to amalgamation. In April 1967 the Territorial and Army Volunteer Reserve replaced the old Territorial Army. The Inns of Court and City Yeomanry was reduced to one squadron and formed part of the “London Yeomanry and Territorials”; the regimental band was retained based at Lincoln’s Inn and attached to the newly formed Royal Yeomanry Regiment… In 1968 the London Yeomanry and Territorials was disbanded, but a cadre of the Regiment, consisting of 3 officers and 5 other ranks, was retained in the Royal Armoured Corps thus ensuring the continuation of the Regiment’s name in the Army List and the retention of headquarters and mess at Lincoln’s Inn. The cadre, however, was disbanded in March 1975. In 1969 71 Signal Regiment (Volunteers) was formed from disbanded yeomanry regiments and on 1 April No. 68 (Inns of Court and City Yeomanry) Signal Squadron was formed with an establishment of 8 officers and 85 other ranks and as such the Inns of Court and City Yeomanry still existed in 1977.
http://www.aim25.ac.uk/cgi-bin/vcdf/detail?coll_id=15900&inst_id=118&nv1=browse&nv2=sub
I’m inclined to think it wasn’t a regiment composed entirely of barristers.
Anyone who’s had much to do with barristers (and I’ve been briefing them for the past 33 years) knows that while there are some nice and gentle souls among them, some of them are arrogant arseholes and many - probably most - have the probably necessary conceit and unbounded self-confidence which isn’t far under the skin of similarly independent professionals, notably surgeons, solely responsible for the consequences of urgent professional decisions which may have catastrophic consequences for others, and occasionally themselves.
The commander of a regiment composed entirely of barristers as ORs, NCOs, and officers would find it easier to herd single-handedly a few hundred feral cats in a thousand acre field. And the feral cats would be more obedient. 
The magic of Google hasn’t given me any info on the background of the members of the regiment, but I suspect that barristers probably formed a relatively small component.
While there were lawyers - both barristers and solicitors - who enlisted as ORs in Commonwealth forces, I suspect many of those enlisted men ended up as officers in combat units.
From wide reading, I get the impression that lawyers were over-represented as an occupational group in intelligence analysis and staff positions, which isn’t surprising given their high degree of analytical skills and attention to detail.
An interesting lawyer/soldier was Ned Herring, who after a distinguished military career in WWI and WWII, with a distinguished inter-war legal career, was recalled from his position as a lieutenant-general in New Guinea to become the Chief Justice of the State of Victoria in Australia.
http://adbonline.anu.edu.au/biogs/A170522b.htm
http://home.vicnet.net.au/~herring/edmund.htm
