Sometime in the early 80s I think, about a group of children (they may have been related) either living in or near a big castle/stately home. One of them discovered a ring, which when he put it on, it stuck for 24 hours, during which time all the statues in the gardens and house came alive, when the ring fell off, one of the other children put it on, and this time it stuck for only 12 hours but again all the statues came alive... and so on. It's been bugging me forever, I really loved it, but can't remember the name of it.