What is the proper way to address a knight?

[mgwatson]

What is the proper way to open a letter to a knight?
For example are these correct:
Dear Sir Roger,
Dear Sir Roger Bannister,
Dear Sir Bannister?

[stellar_fuse]

I'd put "Sir [first name]".

[khackdrums]

You can either address a knight Sir (given name) or Sir (given name + surname). I think the second choice is the proper way of addressing a knight, but the first choice is alright for a fan letter.

Khackdrums

[osiris]

Yes, I'd go with what the others have said too. NEVER Sir + Surname, as the "Sir" is attached to the first name only