Hello,
If someone was convicted of a sexual offence in the country of which they are a national of (not the UK) when they were 18, could that stop them from visiting the UK? Even if it happened more than 5 years ago? 
Are there any waivers available if that person was coming to the UK to visit their partner or if they were travelling with their spouse who is a UK national? 
Any help and advice would be much appreciated.
Thank you