visit visa for unmarried partner of tier 1

[Fairychild]

Hi,

I want to sponsor my unmarried partner for a visit visa to the UK. From South Africa. He recently went back after his working-holiday visa expired. I'm hoping he gets it for 6 months and can stay for 4 or 5 months.

After that we may get married or he may apply for a student visa.

I am not sure what the best thing is to say in my letter for the visit visa. Should I be up front about us getting married after in South Africa and then returning or would that put them off giving a visit visa.

Thanks,