Not sure if procedures have changed but a few years back I found a purse in the street. I dropped it off at the Central Police Station expecting them to just contact the owner. It was an elderly lady and her bus pass was in it so shouldn't have been too difficult to trace her. The Old Bill kept me there while they logged the contents - bus pass, Co-op stamps and not much else. Anyway they told me before I left that if it wasn't claimed in 6 months (IIRC) then I could claim it!
I shook my head in despair and left. However, a couple of weeks later I received a letter containing a £5 postal order in which the lady said she went to the Police station on the off chance it had been handed in and was surprised to find it had been. If she hadn't chased it the Old Bill would have just bunged it in a store room somewhere. Next time I'll do my own detective work and find the owner myself.