There was no yeomanry or cavalry regiment whose name contains the word Ulster and so you don’t create a brick wall for yourself, a little explanation may help.
Remember that prior to 1922, the whole of the island of Ireland was part of the UK and ALL Irish regiments were part of the British army and therefore the following reference to the N & S of Ireland are related more to the northern and southern halves than what we know today as Eire and Northern Ireland.
Following the Boer War in 1902, the Irish elements of the Imperial Yeomanry and other Irish veterans who had served in non-Irish units of the IY, were formed into the Southern Irish Imperial Yeomanry and the Northern Irish Imperial Yeomanry. Then with the creation of the Territorial Force in 1908 that excluded Ireland, the two Irish Yeomanry units were transferred to the Special Reserve and re-titled South Irish Horse & North Irish Horse; the former having the shamrock as the main emblem of its cap badge and the latter the Harp. After WWI the North Irish Horse was disbanded in 1919, but reformed again in 1922, but like with most Irish regiments of the British Army, the South Irish Horse was disbanded in 1922 following the partition of Ireland.
Back to the photograph, as I said the cap badge limits the number of mounted regiments it could belong to. I know on the face of it the letters look remarkably like RUY or BUY, but that must be a trick of the light & shadow as there are no regiments of the British army whose name began with those letters. I’ve tried to track down a clear photograph of pre-WWI shoulder titles for the Royal Wiltshire Yeomanry, but like on the web (search or images) I can only find the post 1920’s version that is just the 3 letters RWY.
Going back to my original post, I made a mistake saying the uniform was post 1908, I had my dates mixed up, as I said above1908 was when the Territorial Force was created and the Yeomanry became TF cavalry units, the khaki service dress was introduced in 1902 following the army’s experiences in the Boer War.
Having made that correction, and rechecked the uniform details and the tunic jacket in the photograph shows features that would make it a WWI “simplified pattern”. There are no rifle patches above the breast pockets and the pockets themselves are lacking the centre pleat; these simplified tunics were created and issued during WWI not before it.
There were a number of regiments, (infantry, cavalry etc.) that were posted to Ireland during WWI. Interestingly in addition to its original 1st line unit, the Royal Wiltshire raised another 2 units, the second line 2/1 & 3rd line 3/1 Royal Wiltshire Yeomanry, both of which were reserves training replacements for their lower numbered counterparts. Early in 1918 the 2/1 RWY moved to Ireland (Dublin) I don’t have any details of the units post WWI duties, but certainly mounted units were in Ireland through to Partition in 1922.
Unfortunately, if he only served in the 2/1 RWY and didn’t see overseas service in a theatre of war, he wouldn’t have received any WWI campaign medals, however as there are 126 WWI Medal Index Cards for Corporals, 33 Lance Corporals, who served in the Wiltshire Yeomanry, if you have a name you should still try searching for a WWI Medal Index Card either on Ancestry or the National Archives web site.
Assuming he either enlisted or was conscripted into the RWY, it’s possible he volunteered to enlist into a regular cavalry regiment after the war, there was a financial incentive to so. Re-enlisting and going on to serve after the partition of Ireland in 1922 could be what gave rise to the story he served in Northern Island. If that was the case any service record will still be with the MoD, but without a service number it will be far from guaranteed you would have a successful application. There are also rules about next of kin and proof of death, see https://www.gov.uk/requests-for-personal-data-and-service-re...