The claims of the Swiss-based consortium which owns the painting are supported by Professor Alessandro Vezzosi, who has set up his own art museum in Vinci. He will present evidence alongside Professor Carlo Pedretti of the Armand Hammer Center for Leonardo Studies at the University of California. The Isleworth Mona Lisa was discovered shortly before the First World War by Hugh Blaker, an English art collector, while looking through the home of a Somerset nobleman. He bought the painting and took it to his studio in Isleworth, London, from which it takes its name.

Art critics conjectured that Leonardo had in fact painted two portraits of Lisa del Giocondo, with one hanging in the Louvre and the other now with Mr Blaker. He in turn sold it to an American collector, Henry F Pulitzer, who in turn left it to his girlfriend. On her death, it was bought by a consortium of unnamed individuals who have kept it in a Swiss bank vault for 40 years.

But despite claims the Isleworth Mona Lisa is indeed the work of Leonardo da Vinci, Martin Kemp, emeritus professor of the history of art at Oxford disputes this.

'So much is wrong,' he told The Sunday Times. 'The dress, the hair and background landscape. This one is also painted on canvas, which Leonardo rarely did.' Like the majority of his works, The Mona Lisa in the Louvre is in fact painted on wood. And while the lady in the Isleworth Mona Lisa does appear to be a younger version of the model in the more famous painting, Kemp said this did not prove the two were produced by Leonardo da Vinci. 'She might look younger but this is probably because the copyist, and I believe it is a copy done a few years after the Mona Lisa, just painted it that way,' added Mr Kemp.

I think it was done by Ceilia Gimenez.

You probably were not summoned to give an opinion on the Salvator Mundi - now accepted (?) as by Leonardo (certainly by Kemp) - but that is apparently owned by a US 'consortium of art dealers' - therefore a 'dud'?