Last night’s airing of BBC’s Fake Or Fortune – which sees Fiona Bruce and several art experts investigate the provenance of potentially valuable works  – proved that a painting denied by Lucian Freud to be of his hand, to in fact, be his.

The painting had been knocking around the art world for the last 30 years, but owner, Jon Turner, had never had any success in getting it properly examined – as was pointed out in the show, he’d spent his time having “doors slammed in his face." This is mainly due to the fact that before his death in 2011, Freud had vehemently denied painting The Man in the Black Cravat, as it had fallen into the hands of one of his (many) enemies, the artist Denis Wirth-Miller – who had studied with Freud at the “bohemian” East Anglian School of Painting – and in turn gave the work to Jon Turner.

But after in-depth investigation by the Fake or Fortune Team – trawling through archives from Freud’s school, analyzing the DNA of a hair found on the painting (not his), speaking to his daughter Rose Boyt (who didn’t provide much more evidence, other than it was highly likely her father just didn’t like the painting and wanted nothing to do with it – as he certainly didn’t like Wirth-Miller – and she respected that).

Then breakthroughs begin with Freud’s former solicitor, who had had discussion’s with him about the painting – making notes that he had admitted to starting the painting but not completing it. After further analysis of the painting: the brush strokes, pigments etc. by an expert; she believed it to all be by one hand.

Corroboration from the art world was finally received as two out of the three experts brought in to attribute the work were happy to say that the painting was entirely by Freud (as Christie’s had said in 1985 before retracting that statement after Freud’s denial), possibly in 1939 at art school; the third expert who is compiling Freud’s catalogue raisonné was slightly more cautious, and said he believed the work to be by Freud, but the background to be unfinished and not designed for display, so was not prepared to put the work in the full catalogue but would mention it on the appendix – which is more than Turner could have imagined before the programme, as with Freud’s refusal to authentic, Turner had been unable to sell the work under his name. Now, the painting is valued between £300,000 – 500,000.

Before Wirth-Miller died, he told Turner, "I want you to sell this picture as publicly as possible. I want you to humiliate Lucian Freud.” – he’s certainly on the right track.

Philip Mould, an art expert who presents the programme alongside Fiona Bruce, said: “It was a novel and gargantuan task to overturn the reported views of the artist. It was different from anything we’d taken on until now – we had never had to arm wrestle with the words of an artist beyond the grave.

“It was all the more frustrating as the more I worked on the picture and Fiona was able to add the background with her enquiries, the more I felt confident about it being entirely by Freud.”

Click here to watch the episode in full (UK residents only)