Brian Worthington, who taught me English at Clifton College boarding school in Bristol, introduced me to the great intellectual love of my life: Shakespeare. He was also the first person to suggest I become an actor.

My first encounter with Shakespeare was aged 8 at St Paul’s Cathedral School in London, when John Llewellyn, the headmaster, asked me to read aloud Mark Antony’s part from Julius Caesar. I thought, “God, this is fantastic”. I can still remember where I was sitting in the library and the way the sun beat down on my desk. So I have to thank John for this, but it was Brian who went on to nurture my interest and got me to study Shakespeare properly.

He regarded English as a severe discipline and he was very strict, which is unusual for a popular teacher. He had firm opinions about literature, which was quite exciting for adolescent boys. I remember before an A-level exam, he said: “There’s a choice on this paper between Hardy novels and Shakespeare sonnets, and if you choose Hardy novels, I will not teach you.”

He directed the school play and cast me as Desdemona in Othello in my first year, and then wrote me a letter of congratulations. I was in the play every year after that.

After my O levels, I met the teachers with my parents and Mr Worthington said, “I wonder whether Simon’s thought of going into the theatre”, which was rather extraordinary, as he wasn’t a fan of professional theatre. I lacked confidence as a child and until that point I hadn’t considered making a career out of acting. I remember having dinner one night with the other boys and they were all being very funny, and I sat there thinking: “You’ve got to try harder. You can’t sit there silent like a great big lump.” I did have friends but I felt I wasn’t quite clever enough. Acting allowed me to show off and I realised I was good at it.

Because my family were doctors, I chose three sciences for my A levels. During my first chemistry class, Brian rushed in and said, “You’re an absolute idiot. Your best subject by far is English and you shouldn’t be doing chemistry.” He was right. So I changed. And while I’d like to pretend I dazzled with natural talent, I worked very hard at my English.

When I was 17 and in the Oxbridge term, Brian astounded me by saying, “I think you should play King Lear and I should direct it”. I said: “You must be joking, sir, I’ve got big exams.” But he wasn’t having any of it, so we did Lear. Two years ago, I was learning Lear and I realised I knew it. My brain had retained the words.

I do keep in touch with him and I see him occasionally. I don’t have to tell him how influential he was. It took me about a year to call him Brian instead of sir, let alone say anything sentimental like “you changed my life”. But he knows.

I wouldn’t have been an actor if it weren’t for Brian. He once gave me a sonnet to read and said, “You have that actor’s instinct where you can sense something, even though you have no idea what it means”. And he was right. He sounds tough, but he was very kind. I was never under pressure with my exams and I never felt judged. When I told my parents I wanted to be an actor, they said, “Thank God for that”. Nobody was surprised.

Simon Russell Beale was talking to Kate Bohdanowicz. The Tempest, in collaboration with Intel and in association with The Imaginarium Studios, played at the RSC from 8 November 2016 to 21 January 2017 with a free live schools broadcast planned for on 30 March 2017. For details, go to rsc.org.uk