St Giles's Pound was an old landmark, removed in 1765, and a point from which distances to London were measured.
It was located in the parish of St Giles-in-the-Fields, close to the boundary with St Anne, Westminster. It was originally located in the middle of St Giles High Street, but was moved in 1656 to the corner of Tottenham Court Road, Oxford Street and St Giles High Street.
It is mentioned in an old song "On Newgate steps Jack Chance was found, and bred up near St Giles's Pound".
References
St Giles's Pound Wikipedia(Text) CC BY-SA