Large sums of money remain unclaimed by Australians. These sums are held in Post Office accounts and many thousands of Institutions in the UK. Sums outstanding go back as far as 1840 and in a few cases before Queen Victoria came to the thrown.
I've brought it back as a subject having followed missing sums supposedly owned by a Great Uncle who died in Brixton in London in 1957. He ended up in London after being wounded at the Somme in 1916 and never returned to Australia.
I found out that he lodged a nomination form with the Post Office in 1936 (filled out by poorer people or those who did not wish to make a will). He was given back the original which must have been lost. I found out the Post Office still retained a copy.
A sum for £18,768.68 was paid out in November 2009, 52 years after his death, and is being shared amongst 11 relatives.
You can start a trace online via http://www.mylostaccount.org.uk
I believe about £4 billion (A$7.3 billion) is still being held. Most people wont bother but the internet has made the task a lot easier.