The house flag of the Clyde Shipping Co. Ltd, Glasgow. A blue pennant with a white lighthouse standing on a rock and the initials 'C. S. C.'. From 1860, the company's ships were named after lighthouses and lightships. This flag design was introduced in 1924 following a suggestion made by Miss Blakiston-Houston. The previous house flag consisted of two red-bordered pennants with the Scottish lion above the Irish harp. It was changed to avoid offending national sensibilities. The flag is made of a wool and synthetic fibre bunting. It has a cotton hoist and is machine sewn. The design is printed. A rope and toggle is attached.

The shipping company started in 1815 with small steam vessels carrying passengers and towing lighters on the Clyde. Soon afterwards it began running passenger services across the Irish Sea and down the British coast to Liverpool. The business was bought by the Kidston brothers in 1856. This co-partnership was dissolved in 1893 for the purpose of starting a limited liability company. After 1860 it was decided to name the firm's coasters after famous lighthouses and lightships. The company fleet in the 20th century included tugs, coasters, and ocean-going tramp steamers. The coasters traded between Scotland, Ireland and England carrying cargo and passengers. The company is still in business as a Glasgow-based, leisure marine group.