In 1975 a worker at the car firm Fiat went along to an auction of lost property organised by the Italian national railway in Turin.

He paid 45,000 lira (£32 – equivalent to about £300 today) for two paintings that caught his eye – one a still life and one an image of a woman relaxing in her garden.

For almost 40 years, the man – whose name has not been made public – kept the pictures hanging in his kitchen. They accompanied him on his move, post-retirement, to Sicily. At no point until last year, believe Italian police, did he realise quite what a bargain his purchase had been.

Now it has emerged that the paintings are stolen works by French artists Paul Gauguin and Pierre Bonnard, and the first – a still life dating from 1869 – has an estimated value of between €10m and €30m (£8.3m to £24.8m). The second, entitled La femme aux Deux Fauteuils (woman with two armchairs) is believed to be worth around €600,000 (£497,000).

Stolen in London in 1970, reportedly from the widower of a daughter of one of the Marks & Spencer co-founders, they were unveiled on Wednesday to applause at the Italian culture ministry in Rome.