DRLs, can they be turned off?...

[catso]

I understand that it is a legal requirement that all cars from a certain date must have Daytime Running Lights fitted.

I've read the DFT document (2010) about this but it is unclear to me whether it is a legal requirement to use them, especially as some cars have the option to switch them off.

My question is; if a car has DRLs is it illegal to switch them off?

[catso]

I know some can be turned off, my Wife's old 2013 Citroen could as can my 2014 Audi, however I know many can't - my Wife's 2016 Qashqai for example and obviously many older cars don't have them at all and there is no requirement to fit them, but I'm curious as to whether it's legal to turn them off on a car that has them?

[catso]

Thanks for the replies, I understand all the arguments for and against DRLs and didn't really want to get into a discussion on that, rather was asking about the legality of them being switched off, anybody know?