A sculpture which BBC Fake or Fortune? reluctantly decided was worthless has sold for over half a million pounds after experts later proved it was the work of Swiss master Alberto Giacometti.

In the episode broadcast last autumn, art expert Philip Mould and presenter Fiona Bruce saw the potential of the small abstract sculpture and began to probe whether it was a genuine Giacometti.

The sculptor is one of the greatest masters of the 20th century. One of his bronzes sold for $141 million in 2015 – a world record.

But without a signature or other proof in a market blighted by fakes, the programme ended with the Giacometti Committee being unable to confirm its authenticity.

However, after the original screening last September, layers of household paint were removed from a strikingly stark white square of plaster set with two shallow grooves, uncovering a signature and other evidence, proving that it was indeed a genuine Giacometti.

The sculpture sold at Christie’s in February as an original work for more than half a million pounds, but the news was held back for last night’s screening.