Christmas: Where can I find a 'singing' post box?

Video caption, WATCH: Ever heard a post box sing?

These post boxes might look a bit more Christmassy than normal, but that's not the only reason why they're special.

They SING!

To begin with Royal Mail set up four 'singing' boxes - in London, Cardiff, Belfast, and Edinburgh.

They were so popular, four more have been added - in Glasgow, Liverpool, Manchester, and Birmingham.

Watch this video to have a listen to their Christmassy message.

Have you seen one? Keep us posted (in the comments)!