Churcill's "we'll fight them on the beaches" speech...whos voice are we hearing?

We are familiar with the "fight 'em on the beaches" and other rallying speeches made to Parliament in the summer of 1940. You can hear them in many WW2 doentaries, but there weren't any microphones in the commons until the 1960s. There is no evidence he subsequently went to a recording studio, so who is reading the words? Incidentally his "Iron Curtain" speech made to Congress in 1945 on camera has a very different voice.