The man left. Mr Axford, afraid to let the sculpture out of his sight, slept with it at his bedside. The next morning he gave it to the British police, who've had it ever since.

To follow this story to Mayfair, we must first go back almost exactly 30 years, to the city of Jos in central Nigeria. On the night of 14 January 1987, thieves broke into the Jos Museum. A guard was severely beaten. The thieves knew what they wanted - they made off with nine of the museum's most precious treasures.

In the 1980s and '90s Nigeria's museums suffered many damaging robberies. Staff from within Nigeria's National Commission for Museums and Monuments (NCMM) collaborated in some of the thefts. A former employee at Jos Museum told me she was in no doubt that this robbery was also an inside job. 

The NCMM instantly alerted Unesco, providing photographs of everything stolen from Jos.

In 1990 collectors in Switzerland were approached by a man trying to sell a beautiful Benin Bronze head for a half a million Swiss francs. The collectors were suspicious, and with the help of American, Swiss and Nigerian diplomat,s it was identified as having come from Jos and was returned to Nigeria. 

Meanwhile the other eight pieces had, apparently, vanished. Most of them, including the Ife head, are listed in a 1994 publication by the International Council of Museums (ICOM), entitled One Hundred Missing Objects; Looting in Africa.

It wasn't until many years later, in bizarre circumstances, that the Ife head would reappear, in Belgium.