Immigrationboards.com

Can anyone offer advice for a friend who has a girlfriend who has been in the UK illegally for ten years, she is a non EU citizen but he is an EU citizen who lives in the UK and has done for a long time, owns property and is now retired. Is there any way to make her 'legal' in the UK. Could they get married or would the registry office call the police so she would be arrested when trying to get married? Would she need to leave the country and return under a fiancé visa? What are the options available?

He should first get married to her.

As you already know, in order to marry in the UK the Registrar is legally bound to notify the Home Office. The HO can then extend the notification period from 28 to 70 days to enable them to interview the couple separately should they choose to do so, before the wedding can take place.

An overstayer is at risk of detention during the interview.