Mr Patch worked as a plumber until he retired in 1961

Harry Patch, 109, from Wells, Somerset, was chosen to throw the switch because he helped build the tower as a plumber back in 1925.

He also attended the tower's opening by King George V and Queen Mary.

He remembers placing newly-minted coins under lead covering a trap door at the top of the tower during the ceremony.

In 2005 the University of Bristol awarded Mr Patch an honorary degree in recognition of his work on the university's landmark building and his service in one of the main World War I battles at Passchendaele, Belgium.

Born in Bath in 1898, Mr Patch had a war posting in Rouen, France, in 1917, but returned to England a year later after a serious shrapnel wound left him in hospital.

He has survived his wife of 58 years and two sons.