Only Surviving British Flag from Trafalgar goes on Sale

The Battle of Trafalgar, where a fleet commanded by Britain's Nelson defeated a French force, remains famous in England. Now the only surviving flag to have been flown by the British Navy is to go on sale. According to this Times article, the flag was on the HMS Spartiate, and after the battle was given to Lieutenant James Clephan. It is now being sold by his descendants, after being kept in a drawer to try and protect it. The flag is damaged from the battle, and is expected to make around £15,000. To be honest, if this really is the last flag from a battle so famous in one nation's history, I'd have expected a much higher figure.