I'll come clean. I work for the company that provides Blyk with its age and identity verification solution. 

It's the same technology that is used by the major online gaming companies to screen out underage players.

Basically an organisation like Blyk sets its own pass or fail criteria. Then, if it reaches the 'pass' level using basic personal information (name, address, DoB) it doesn't need to ask for further proof of ID such as a passport or driver's licence. 

It's all about getting the maximum number of good customers through as quickly as possible - and it seems to be working!

It's really the electronic equivalent of having a bouncer on the door keeping out people who don't look like they should be "in the club". 

They can make an instant decision or, if they're not sure, they can ask for further proof of ID.

Why didn't she just say she was a mature student? Surely its illegal now to discriminate on age alone?

I have passed though with no problems, although I am 23. Humm no driving licence, you can get a driving licence from 16, although it cost £42 (€60, US$84)!

I'm 16 and I gave my voting address and that was all it required, no passport or driving license. Maybe only if they have doubts about your address they need to ask.