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thanks Tee2072, I managed to clear the autofill today (back in the office) for some reason clearing autofill didn't resolve it and I went through all the subject line autofills one by one and deleted them in gmail which I hope will resolve it for good!
have a bit of an issue with my work email which is powered by gmail. It seems that mumsnet thread titles I have posted to, appear as suggestions in gmail when typing in the subject line, which is fine but now the assistant for our office at work is going to have access to that email too and will sometimes send emails from my account. The gmail settings are to keep no search history etc. so I don't know how to resolve this.