I recall his surprisingly un-Cornish attempt at Lucky Jack Aubrey in Master And Commander and was therefore unsurprised at his Robin O'Hood :)

An actor has the job of making the character believable and either getting the accent right or dispensing with it altogether is the stock in trade.

By the way if he persists in drawing his bow back out of his eyeline in that fashion I can say as a seasoned archer he will never hit anything. :)