Harman played heartthrob Dennis Rickman, but has undergone a serious transformation since waving goodbye to Walford.
The actor showcased his new long hair as he hit the red carpet at the opening of Agatha Christie's Witness for the Prosecution at London County Hall.
Harman posed for photographers in a denim shirt, leather jacket and brown trousers which he teamed with a rucksack at Wednesday night’s event.
Harman has enjoyed a handful of theatre roles since bowing out of EastEnders when his character died in the arms of his wife Sharon, played by Letitia Dean.
On leaving the soap he told the Guardian: “When I’m 80, I want to sit down and go, ‘Well at, least I tried it’.
“I don’t want to ever say, ‘Oh, if only I hadn’t stayed in EastEnders for 25 years’.”
Harman – who is married to actress Lucy Liemann – played Sky Masterson in Michael Grandage’s revival of Guys and Dolls and Simon Cowell in West End musical I Can’t Sing! The X Factor Musical.
He also played Lord Farquaad in the original London production of Shrek the Musical for which he won an Olivier Award.
Harman also enjoyed TV roles in Hotel Babylon, Downton Abbey and Sky One’s Mount Pleasant.