A woven Red Ensign flag.
The Red Ensign was used by the British Navy for their Red Squadron up until 1864. At that point the Navy as a whole adopted the White Ensign and the Red was used by the Merchant Navy. This flag has a label sewn to it with the name Queensmount. It's possible this refers to Queensmount School in Bournemouth, who being on the coast may have had boats. This is purely guess work though.
The flag is not printed but woven and of a good size. Mid 20th Century.