London Mayor Boris Johnson has imposed on the US President Barack Obama a £120 fine for not paying the congestion charge on his recent state visit to London.

The fine was imposed on the U.S. President’s motorcade after his visit in May. Johnson asked the US president to pay the congestion charge at the rate of £10 per each of the vehicles found in the motorcade. As there are 12 vehicles, he was asked to pay a total of £120 as fine.

The US Embassy in the UK refused to pay the amount like other countries and the small amount of fine on Obama was only a part of the total unpaid amount of more than £50 million owed by diplomatic missions in the capital.

The total unpaid amount by the US has now reached more than £5 million in 45,005 unpaid congestion charges since the scheme was introduced in 2003 by the UK government.

The US embassy, like those of other countries, argues it should not pay because the 1960 Vienna Convention on Diplomatic Relations had prohibited the imposition of this sort of tax on diplomatic missions. However the British authorities say the charge is not a tax but only a charge. The dispute continues.