He certainly had at leat a few plays produced professionally, the last I think being "Hallelujah I'm a Bum" about a gay affair between a prime minister and his minister for family values. He was active in the CPGB until the USSR crackdown on Hungary, and then joined the Trots. In the fifties he was jailed at least once for trade union activities.

I should think that those daily swims were more probably in the English Channel, as he lived in Brighton.