I don't think Secombe ever did {have a proper operatic career} and no-one ever referred to Secombe as an opera singer, mainly because he was more associated with the Goons and comedy on TV/radio,
John W
I recall my dad telling me that Harry Secombe
did audition at Covent Garden but was not given work there as he was not taken seriously enough to be an opera singer. My dad has no doubt though that he had the voice to be one. Wasn't he very short and stout too? That probably didn't help matters since his voice was that of a romantic tenor.