Oscar nominee and old Harrovian Benedict Cumberbatch has spoken out numerous times about “posh bashing”; now his old drama teacher has gone one further by saying that having a private school education can actively hinder a career in acting.

Speaking to the Radio Times, Martin Tyrell, a retired drama teacher with 32 years experience at Harrow School in North London, said “Going to a major independent school is of no importance or value or help at all. I don’t think anyone ever bought an education at Harrow in order for their son to become an actor.”

He said that the prejudice shown towards actors from wealthy backgrounds meant that they would not be considered for roles that they would be perfectly able to play, but are instead type-cast. “I feel that they are being limited by critics and audiences as a result of what their parents did for them at the age of 13. And that seems to me very unfair.”

Cumberbatch, 38, has spoken out a number of times against what he calls “posh bashing”. In 2012 he told the Radio Times that he was considering moving to America, following in the footsteps of fellow public school educated actors such as old Etonians Damien Lewis, who shot to fame as an American Marine in the hit series Homeland, and Dominic West, who played an Irish-American detective in the critically acclaimed series The Wire.

“All the posh-bashing that goes on. I wasn’t born into land or titles, or new money, or an oil rig,” Cumberbatch said, adding that he was often “castigated as a moaning, rich, public-school b*****d, complaining about only getting posh roles. It’s just so predictable, so domestic, and so dumb. It makes me think I want to go to America.”

In 2013 he again hit out at critics, saying “I was desperately proud of my parents for sending me to Harrow. It was a huge stretch for them. They were working actors who never knew when the next payday might come. My parents wanted the best for me. I wasn’t sent to the school my dad went to. I’m not a hereditary peer.”

Fellow actor Lewis has also in the past admitted hiding his background from casting agents “to avoid any typecasting in a floppy-fringed, public schoolboy kind of way”.

Their comments echo those of the singer James Blunt, also an old Harrovian, who recently made headlines with an angry open letter addressed to shadow culture secretary Chris Bryant in which he wrote: “EVERYONE I met in the British music industry told me there was no way it would work for me because I was too posh. One record company even asked if I could speak in a different accent. (I told them I could try Russian).

“Every step of the way, my background has been AGAINST me succeeding in the music business. And when I have managed to break through, I was STILL scoffed at for being too posh for the industry.”