Hadden-Paton played the lead role of Henry Higgins in the Lincoln Center Theater revival of My Fair Lady on Broadway, a performance for which he was nominated for the 2018 Tony Award for Best Actor in a Musical.
He was commended in the 2007 Ian Charleson Awards for his appearances in Romeo and Juliet at the Battersea Arts Centre and as John Worthing in The Importance of Being Earnest, directed by Peter Gill.
His stand-out performances continued with Captain Jack Absolute in The Rivals at the Southwark Playhouse, as Hohenzollern in The Prince of Homburg at the Donmar Warehouse, and as Harry Villiers in the 2010 première of Posh at the Royal Court.
In 2011 he appeared as Teddy Graham in the Olivier Award-winning revival Flare Path at the Theatre Royal Haymarket, and as Jackie Jackson in a film adaptation of The Deep Blue Sea, both marking the centenary of their author, the English playwright Terence Rattigan.
On television, he is best known for playing Bertie Pelham, the Marquess of Hexham, suitor of Lady Edith Crawley on Downton Abbey; their characters were married in the 2015 Christmas special that concluded the series.