[8] He spent several years working on the Irish Law Times with William John Johnston, where he mastered Pitman's shorthand.
During this time, he presided over several notable cases, including: the Seamus Clandillon libel trial (the longest libel action in the history of the Irish courts at the time, running from 29 October to 14 November 1928), the action by the Lynch family following the Copley Street Riot, and the murder trial of those accused of murdering Noel Lemass (brother of Seán Lemass).
[9] On Easter Monday, 24 April 1916, Hanna was on manoeuvres in the Dublin mountains with his battalion of the Volunteer Training Corps, known as the "Gorgeous Wrecks" (a pun on the name of the King, Georgius Rex), when they got word that the city was in the "hands of the rebels".
They have no ammunition to use with the rifles—there is not a bullet in Dublin that would fit them, and under these circumstances I refused as I say to invite attack parading useless, antedeluvian [sic] weapons.
Amidst the chaos, Hanna worked to procure essential supplies for the troops defending Beggars Bush Barracks.
Hanna's enduring memories of the Rebellion included the city aflame at night, the thunderous cannonade, nerve-wracking sniper fire, and an unwavering compulsion to engage with neighbours and understand the unfolding events.
[11][12] Writing in the Irish Independent on 30 November 1918 as a part of this campaign, Hanna voiced opposition to partition which 'would be disastrous to the interests of Southern Unionists'.
Beyond the courtroom, Hanna's interests extended to photography, he was made vice-president of the Photographic Society of Ireland, and canine expertise, he served as the president of the Irish Kennel Club for several years.
[13] In 2015, the National Museum of Ireland staged a theatre show that focused on the fate of the 7th company of the Royal Irish Fusiliers, young Irishmen who were sent to fight in the disastrous Allied assault on Gallipoli in 1915.
The creators drew heavily on the book 'Pals at Suvla Bay', a memorial written by Hanna upon his return from the war, as well as other historical texts.