Now this is very interesting! I am getting the idea that learning maths depends on getting feedback almost immediately, probably at several stages - which cannot be done (at least not as easily) with distance learning. I also suspect that tone of voice, body language and other visual clues are vitally important - and, again, generally absent when you're a hundred miles away from your students.

A lot of my own teaching is concerned with what Henrik described as "quick sums in your head while shopping". Basic Skills, recently renamed Skills for Life, soon to be renamed again to Functional Skills, mainly for adults who had a bad experience of learning maths. (These people are typically intelligent enough in other areas - and I cannot help but admire them for giving up their free time to come and listen to me waffling on about their least favourite subject.) Quite often they need a lot of guidance, patience and reassurance - some are genuinely scared of maths - and there is simply no way I could provide that online. Saying things like, "You're doing fine," "What do you need to do before that?" or "How can we simplify that?" are okay in conversation but don't work so well on the screen.

At higher level, I imagine the reassurance isn't so important - the fact that the students got to the higher level suggests they have a reasonable understanding of the subject - but teaching it online does sound a lot harder.

Incidentally, I recently met a woman called Jo who teaches geology online. Quite a few of her students are from Other Cultures, and do not approve of women teaching; but they also don't realise that Jo is a woman's name, so she doesn't bother to tell them.