That long-awaited marriage between Britain’s illustrious Roya1 Shakespeare Company and CBS finally will be consum mated Sunday night when the network offers the RSC’s production of “A Midsummer .Night’s Dream” on (Channels (2) and (9) at 9 p.m.). This is the Cecil smith first in an annual series — Shakespearean plays to be produced by the great British troupe for CBS, and to launch the series director Peter Hall corralled some of the RSC’s most famous players, among them David Warner, Diana Rigg, Ian Richardson, Paul Rogers, lam Holm and Judi Dench. But the play the heroine Hermia, Hall selected relatively unknown 23-year-old Helen Mirren, a pert, blonde lass currently playing in the second annual RSC season in the Ahmanson Theater of the Los Angeles Music Center. And how did Helen find acting in the “Dream”? “Terribly unco mfortable,” she said. To work in such an august assemblage of actors? “Oh, no, that was smashing,” she said. “And to work with Peter Hall in my first film was thrilling. But you know Peter He didn’t want a nice, idyllic iAthenian midsummer. Oh, no! He wanted an Elizabethan mid summer, a cold, damp, foggy, English midsummer.

‘So he shot it out of doors in November. Diana and I wore these short cotton dresses — minidresses, really It was bitterly cold. ‘And muddy! That’s what our makeup was. Mud. Before every shot someone came over and shoved a great gob of cold, English mud on our faces and smeared it all over. Then they sprayed our dresses with icy water so they’d cling to us. It’s authentic, I suppose, but it was damned uncomfortable.” Volumes have been written about the Royal Shakespeare’s striving for authenticity, about shifting its actors between classical and starkly modern plays to give the classics con temporary meaning, about the rigorous training and disciplines of the troupe that make it unquestionably the finest act ing company in the English speaking world. But Helen talked of something she found with the RSC which she calls its “bravery. “It was really awfully brave of them to take a chance on someone like me in so im portant a production,” she said. “That’s what they do with their young people — shove them into very important parts, sink lor swim. That’s how David and Diana and the others got started. “Two years ago I was in college, training to be a teacher. I always wanted to act, of course, but there didn’t seem much chance. Then after college, I got on with the Manchester Repertory, and then quite suddenly the Royal Shakespeare offered me a contract. “They gave me leading parts right away. They took me to Moscow and Leningrad and Helsinki on the Russian tour. They put me in the ‘Dream.’

What a two years this has been! After the ‘Dream,’ Michael Powell took me to Australia to do the movie, ‘Age of [Consent,’ with James Mason. Last month, I was playing in London. Here I am in Los Angeles. We’re going on from here and play San Francisco, Det r o i t, Cleveland, Baltimore, New Haven. “It really bowls a girl over from Leigh-on-Sea in Essex. She looked terribly young, curled in an armchair in her hotel suite, legs in long char-, treuse stockings drawn up un-l der her, a red velvet ribbon in her long, blonde hair. Aside from the still-unre leased movie she made with James Mason, in which she plays “an ignorant beachcomber kind of girl,” she’s done nothing but Shakespeare in her brief professional career. Between performances, she’s exploring America with | great glee. An orange Peanuts sweatshirt she bought for her English boy friend hangs over a chair. And she sent him “a card of the greatest American baseball player, Baby something, a little round face and bats.” Eagerly as a high school girl, she was looking forward to a soccer match between the Royal Shakespeare actors and a UCLA team. “Only one thing bothers me,” she said. “Teaching. All that training I had, gone to waste. I really should try to do some teaching…”