A central pillar of the Liberal Democrats' general election campaign - a local income tax - was put to the test by David King of Stirling University, writes Paul Hill.
Professor King, who has worked at Stirling since 1978 and who now holds a chair in public economics, was first asked to examine the party's local tax policy in October 2003.
He was asked to calculate how the policy would affect households in different local authority areas across England and Wales - an exercise that he repeated in 2004.
"I wasn't concerned with the administrative practicability of the scheme, just what the income tax rates would be in each local authority," Professor King said.
"I gave them the 2003-04 numbers and the 2004-05 numbers, but there didn't seem to be any fundamental change to the policy as a result of the information that I had provided," he said.
Professor King, who is not a member of any political party, has worked as a consultant to organisations such as the Council of Europe, the Organisation for Economic Co-operation and Development and the World Bank.
He also spent a year in the 1980s as an adviser at the Department for the Environment, advising Margaret Thatcher's Government about the poll tax.
"What I love is local government finance, and I would advise anyone in any country or of any political complexion," Professor King said.
"I advised the Gorbachev Government in the 1980s too, so I've even gone as far left as the Communists."