Im sure there was once one the other side of gas hill , spent a long time seaching ketts heights top to bottom , found nothing but brambles! also a little further along on or under ketts hill there was one or more as sometime ago the back of a house went into one , it was reported in EDP etc at time but cant seem to find the paper cutting. if you seach the EDP (maybe at library as i dont seem to get no joy on web) over the years their has been various reports on the mines , loads around the time the bus went in the earlham one i think may 1984 ( Guess?)