It's not too hard to google up more documents about Dr Press and this whole business - well worth reading. This is a long interview with Tim Jenkin, one of the ANC's other technical boffins in the UK:
> Our concern became how do you run and how do you operate an underground war by remote control without any contact with your soldiers? It's like running a war with no communications and no-one's ever won a war like that. The prime weapon in any war is your communications. [...] so we bought into it and started using computers from the early eighties. By today's standards these were hardly computers but you could type things on them and you could print them out and you could ultimately produce publications. It was a big step forward and I was in it right from the beginning. The PC itself came on the market in 1982 I think it was so right from that time when the first PCs became available. In those days computers couldn't really do an awful lot. You'd have a word processor and that's all it could do for that moment while you were running the word processor. So if you wanted to do anything else you had to learn how to programme it yourself.
> We got into that, learnt how to programme these things and immediately we could see this application. Whereas before we'd done all this coding by hand, adding numbers together and doing all kinds of strange things with books and so on, why not get the computer to do this. You type in your message and it's done and you press a button and it enciphers the thing and produces a string of non-readable characters.
We're all used to the idea that there is a secret history of World War II fought by geeks in huts in Bletchley Park, Bawdsey Manor, etc. Somehow it still comes as a revelation to me that there was a similar technical strand in the struggle for liberation in South Africa. And it does make me laugh that it was fought from bases in Bristol Polytechnic and a flat in Camden. The compiler is mightier than the AK-47!