Daniel Radcliffe says his girlfriend Erin Darke is his ''best friend''.

The 'Harry Potter' actor has opened up about his relationship with actress - who he met on the set of 'Kill Your Darlings' in 2012 - and he explained their romance is the kind he always ''aspires'' to have.

He told UsMagazine.com: ''I think that's the kind of relationship I always aspire to have with someone I'm in a relationship with.

''You want that person to be your best friend. In the case of Erin, we definitely are.''

Meanwhile, Daniel insisted he doesn't ever try to start a relationship in a certain way but being friends and becoming partners is ''often a very natural'' progression.

He added: ''I don't think you can ever control how anything starts.

''It's not like I seek out that way of meeting people or think I have to be their friend first but I think it's often a very natural thing to progress from into a relationship.

''The whole modern idea of 'friend zone' and all that stuff - that's a word I don't like very much.''