If your partner is already in the UK and is an overstayer, he cannot apply for a fiance visa, unless he returns home and makes an application for entry clearance.

If you and your partner have children together and the children are british, he may be able to make an application for discretionary leave on the basis of the children.

Alternatively, he may be able to make an application for indefinite leave to remain on the basis of 14 years long residence, providing he can evidence the fact that he has been here for that amount of time.

Should you wish to discuss this further please feel free to contact us at info@salamimmigration.co.uk

Regards