i can however say two things in my defence; first, the proof i shall give is probably not a new one; second, if my proof is new it has a certain advantage over other proofs in using only the most elementary arguments.

Make this proper case
I can however say two things in my defence; first, the proof I shall give is probably not a new one; second, if my proof is new it has a certain advantage over other proofs in using only the most elementary arguments.