British Muslim girls being forced into marriage via internet

[muriel_volestrangler]

33. Yes, the UK doesn't give visas for spouses until they're 18

If you are from outside the European Economic Area or Switzerland and want to join your partner who is a British resident it is likely you will be expected to apply for a ‘family of a settled person’ visa.

In order to apply for a ‘family of a settled person’ visa you will first need to show you are eligible to apply.

To apply for this type of visa you must be able to prove:

you are over 18
your relationship with your partner is genuine – either you are married or in a recognised civil partnership, have been living together for at least two years or are engaged to be married or to become civil partners
...
http://findlaw.co.uk/law/immigration_emigration/marriage_visas/apply-for-a-visa-as-the-partner-of-a-british-resident-when-based-outside-the-uk.html

For a few years, the age was 21, but the courts overturned that as affecting genuine marriages:
http://www.bradfordlawcentre.org.uk/news/new-policy-guidance-marriage-visa-age-21
'Common law marriage' hasn't been legally recognised in England since 1753: http://www.lawpack.co.uk/cohabitation/articles/article1585.asp