Upvote:1
In addition to @Traveller's answer, I can state that from personal experience you cannot do it. When my wife and I got married, she did enquire with the home office and it was confirmed that she had to leave the UK and apply for the spouse visa from her home country.
Upvote:3
No, switching from a Standard Visit visa to a Family visa while in the UK is not allowed. See under βWhen you cannot get a family visaβ here https://www.gov.uk/uk-family-visa