Is this taxable?

Yesterday I was given a large gift box that clanked a bit... (I wonder what it can be :-) ) as a thank you for spending half an hour a week chatting with a sixteen year old and helping her with her English homework. When I was asked if I'd be at home on Wednesday at 8pm it never occured to me that the family was bringing me a present, but it's very much appreciated!

Unfortunately Steve's told me I can't open it until Christmas. I wonder if I should declare this to the taxman...no I think not!