My partner has found out at a sexual health clinic today he may have gonorrhoea. they said it may undiagnosed for years without realising is this true?

Very unlikely: Untreated gonorrhea in men usually clears up within a few months, without treatment. It can be carried longer in women, but still rarely more than a year. If you've been together less than a year, one of you might have had it from a previous partner. But gonorrhea in a couple usually means one or the other had another partner in the previous 1-2 weeks. You need testing and treatment. Good luck!