I'm putting this in 'for sale' rather than 'lost and found' because there's probably zero chance of locating the person who actually lost it. But I bet the former owner isn't the only one who's lost one, so it seems a shame to bin it.
Nikon lens cap - it says on the back 'LC-77' and '77mm'.
Free to anyone who can make good use of it (couple of quid in an MRT collecting tin for good karma at your discretion), it's in Sheffield but I'm happy to post it.