Travel to UK on non-EU passport with Naturalization cert

[sindbad]

Hello,
I need to travel to UK and do not have current UK visa. I am travelling from Ireland. I will receive my Irish Naturalization certificate on next ceremony and I'm travelling after two days of that. So would not have enough time to get Irish passport prior to Travel to UK.
Can I travel to UK without visa but in possession of Irish Naturalization certificate with my own non-EU passport? My original country of origin allows dual nationality with Ireland so I wouldn't be doing anything illegal by using my previous passport which wouldn't be expired.
Thank you for your help and informed guidance.