Thank you all for the comments. The reason I mentioned this is that on this particular trip there was a subtle (or at times not-so-subtle) pressure on us re what we were expected to give and mention of an amount that "would be considered an insult". Both the driver and guide were, I emphasise, excellent and would have been given good tips in any case but I know that several other travellers found the "hints" annoying. Also, if everyone gave £20, that is a total of £480 tax free on top of a salary which, admittedly, may be small, but surely what we are meant to give is a "tip" and not part-payment of their salary???? I paid the recommended amount, of course, but I think it is a flawed system.