Barnard, who starred in the role of Melchior Gabor in the musical adaptation of German playwright Frank Wedekind's play, won the award for best actor in a musical or entertainment. He beat the likes of seasoned performers Rowan Atkinson, Bob Golding, Tony Sheldon and Alexander Hanson.
Iwan Rheon, recognisable to fans of E4's hit show Misfits, won his Olivier Award in the category of best supporting performance in a musical or entertainment for his role of Moritz Stiefel. He triumphed over Sheila Hancock, Maureen Lipman and Kelly Price for the coveted gong.
Read more on the Welsh winners and browse the full list of winners on the BBC News website.
