Have a look at the Knightson Computer - it is the easiest to use navigation tool I have ever seen, no moving parts, no batteries and for diversions (and indeed main planning) a no brainer. And, as far as I know, it is approved by the CAA for use in the skills test.
I don't really understand why it isn't better known!
It costs £10 and you can get it directly from the inventor Mark Knight -
www.knightson.org.uk
I don't work for and I'm not connected to them, so hopefully not breaking any pprune ad rules by posting this, but I have just been so impressed with it!
It is so simple.
