In a Port with a trading history of two thousand years, a quarter of a century may seem a petty span. Yet when more has happened to the Thames in that short time than in any hundred years of earlier life, the period deserves to have its record. On the last day of March, 1909, the Port of London Authority took charge of the tidal reaches of the Thames and of the Capital's Docks; and after a quarter of a century's hard work they have re-built the sea-gate of the world. This booklet attempts to sketch the Authority's achievement, to give some account of the historic river they administer, and of the mighty City they serve. A. B. March, 1934.