Tiernan is a writer, stand-up comedian and constantly tired parent. He has performed stand-up for nearly twenty years, including stand-up for children as part of the Comedy Club 4 Kids which he co-runs. As part of this he also writes and hosts the Radio Nonsense podcast for children aged 7+, which now has global listenership and children emailing him most days with questions like 'Why don't cats burp?'

Tiernan has written for TV including Frankie Boyle's New World Order on BBC2, live shows, other comedians' tour shows, podcasts including the popular Super Great Kids Stories, articles and anything that anyone will let him do so he's not just wasting time on Twitter. He has toured a solo kids stand up show around the UK, as well as an Arts Council Funded childrens theatre show called 'How Does This Politics Thing Work Then?' co-written with Tatton Spiller at Simple Politics. He once somehow won an episodes of The Slammer on CBBC and has worked as the TV warm up for Dick & Dom. Most recently Tiernan was commissioned to write episodes for the upcoming 4th series of Studio AKA's Hey Duggee which means all those hours of it he's watched with his daughter can now be classed as 'research'.