shifty's mouth

To tell a lie or tall story. Originates from Rush Green in Romford, Essex. Shifty is a well known exaggerator from that area, and the term "Shifty's mouth" or " to Shifty" has also been heard as far as Ramsgate in Kent, England.

He told me he was at the pictures last night, "Shifty's mouth", he was with me all last night.