I'm currently writing a little screenplay set in rural Ireland in the 1920's, the main character is a member of the R.I.C, and I was just curious to whether they would have been more likely to smoke a pipe, cigars, cigarettes ect.
I'm guessing most wouldn't have the knowledge specifically for Ireland but even what was the most popular in England or the continent would be great.
Not sure about the rest of Europe, but specifically in rural Ireland in the 1910s and 1920s it would be pipe and cigarettes.
Even more specifically, especially amongst the less well-off, it would be a locally-produced short-stemmed clay pipe, known as a dudeen (an Anglicisation of the Irish word dúidín). You can find this word used in Sean Treacy and the 3rd Tipperary Brigade (published 1945, writing about the events of 1919-21), and also in the poem The Black Dudeen by Robert W. Service.
An evocative colloquialism for the dudeen was jaw-warmer (cited in an academic study called Irishmen or English Soldiers, Thomas P Dooley, 1995, where the pipe is enjoyed by the wife of the book's subject, a working class Waterford man who enlists in the British army in 1916) - pipes were smoked by both men and women in less wealthy Irish communities.
Pipe tobacco brands at the time (British but I suspect available in Ireland too) included Carlyle, Player's Navy Mixture, Chairman and Three Nuns (this comes from Tea, Rum and Fags - Sustaining Tommy 1914-18 by Alan Weeks, 2009)
Cigarettes became very popular during WW1, so they were common in Ireland too at this time. The famous Woodbine were quite cheap, with better brands being Players and Goldflake (usually costing sixpence for 20). Inferior quality cigarettes (issued to British troops at times during the war) included Red Hussar, Ruby Queen, Oros (usually called 'Horrors') and Flag.
The most common slang term for a cigarette was by far the still-used word fag. The term gasper referred to a cheap cigarette, but was pre-1914 civilian slang and used mainly by British officers and the wealthy - you'll hear it used by Bertie in Jeeves and Wooster, set in the 20s - your RIC man wouldn't use it.
One last thing that springs to mind... the superstition of the Third Man became powerful and universal in British and Irish troops during WW1: the belief was that the third man to light a cigarette from the same match would inevitably be killed then and there or soon after; anyone attempting to go third man would have his hand or face violently pushed away.
Hope that's helpful. And best of luck with the screenplay!
What years are you referring to when you say the 1920s? The RIC was disbanded shortly after the signing of the Treaty in Dec 1921 and the Civic Guard was established in 1922. In August 1923 the Civic Guard became An Garda Síochána the Irish police force which exists to this day.
The years before this in the 1920s, 1920 - Dec 1921 would be the Irish War of Independence.