Where can I watch Luther??

[MozzchopsThirty]

Really want to watch this before new series starts!

I know I have 3 series to catch up to

Have tried googling but sites I try either bring up lots of adds or games, or want credit card details!
Surely it can't be that hard to watch a BBC tv series online?

It's on Netflix I think

I didn't even think to look there!
It is, many thanks

Also on Amazon prime if you have that.