Apple for the teacher

I met my neighbour a recently qualified schoolteacher struggling home the other afternoon laden down with a large box full of bottles of wine and other end of term 'presents for teacher'.
My idle question as to what the tax liability was on these presents was met with a look of incredulity and the statement that he was not sent a tax return. I semi-jokingly suggested that he might like to ask his colleagues for their advice in this matter. However this did start me thinking that a substantial number of such 'gifts' must be made each term and I have even noticed my local supermarket selling mugs inscribed 'to the best teacher in the world'.
In readiness for any further questions from my neighbour I wondered if readers might give their thoughts as to the tax and National Insurance implications of these...