From the link provided by Barbara Tomlinson of The National Maritime
The house flag of Huddart Parker Ltd, Melbourne. A rectangular, red flag with a blue saltire. The letters 'HP' in white are at the sides. The flag is made of a wool and synthetic fibre bunting. It has a cotton hoist and is machine sewn. A rope is attached.
Originated 1876 as Huddart, Parker & Co. Pty. Ltd. with a similar flag but having the additional white letters "&" and "Co." in upper and lower quarters respectively which was changed to the simpler version after 1912 when the company went public as Huddart Parker Ltd. Its fleet was disposed of in 1961.