The 19-year-old rejected the Town’s offer of a new contract that was made at the end of last season, and has opted to move to Griffin Park with the two clubs agreeing a compensation fee.
Arthur joined the club as an Under-9 and signed a professional contract soon into his first year as a scholar.
He leaves having made seven senior appearances – all in the Checkatrade Trophy – in which he netted once, against Southend United at Kenilworth Road last term.
All at Kenilworth Road wish Arthur the very best at Griffin Park and for his future career.