I've got an antique Sheffield pocket knife (actually a fleam) which has a horn handle. The horn has become dull and lost its polish over the years.

Anyone know what I should use to polish it again?

Or is there still some old penknife workshop that could do it for me?

Try the little mesters workshops at Kelham Island.

That's a good idea. Is Kelham Island open again yet?

As far as I know yes. Even when the museum is closed the workshops are still running as they are actual businesses, if you go to the door at the left of the Bessemer Converter there is a bell for 'Mick the Grinder' (that's if he is still there, haven't been for a while)