Most of the plaques sold by the museum have been bought by Nigeria, says a 1972 report which has only now been declassified.

The Nigerian Government has called several times for all the 700 bronze plaques to be returned.

The revelation is an interesting one for those campaigning to see the Benin bronzes return to Nigeria - and the Elgin Marbles to Greece.

The museum now regrets the sales, reports The Art Newspaper.

In 1950, the keeper of ethnography at the museum, Hermann Braunholtz, told the trustees that of the 203 plaques acquired from the Foreign Office in 1898: *About 30 are duplicate specimens, and therefore surplus to the Museum's requirements.*

If there were two bronzes with a profile of a leopard, one was deemed to be a duplicate, even though they were individually modelled and cast.

'Curse'

The Nigerian Government was interested in buying the pieces but, because the museum did not know how much the plaques were worth, it sold four to a London dealer as a test.

The four went for £1,100, with the museum receiving £876 after deduction of commission.

The following year 13 plaques were sold to the Nigerian Government for £1,050, an average price of £75.

The sale was stopped in 1972. The museum's African specialist, Dr Nigel Barley, admitted the decision to sell was unfortunate.

*From a curatorial point of view, it was a curse. The bronzes were cast in matching pairs, so it is difficult to exhibit them properly,* he said.

The fate of the plaques sent to Nigeria are in doubt as little of the collection of Benin bronzes is currently on display.

Earlier this month Nigeria's lower house of parliament called on its president, Olusegun Obasanjo, to request the repatriation of all the artefacts.

The sale of the plaques could also have relevance for the fate of the Elgin Marbles.