LONDON (AP) — Britain says it will ban the sale of ivory, no matter how old, to help protect the world's elephant population. The government said Tuesday that the ban is the toughest in Europe and will impose a maximum five-year prison sentence for offenders.Environment Secretary Michael Gove says "the abhorrent ivory trade should become a thing of the past." There will be exceptions for some old musical instruments and for works of art, such as portrait miniatures, that are more than a century old.Conservationists say about 20,000 elephants a year are killed for their tusks.