The picture, brought back as a holiday souvenir, has been unveiled in public for the first time and looks set to fetch at least £10,000 at auction next month.

Its story had been kept a family secret for over 100 years, hidden by Mrs Sheersmith's relatives until they entered it into a British auction earlier this year.

The New Jersey seller, who wishes to remain anonymous, said the picture had been picked up by her great great aunt on her regular trips to Europe.

She said her kindly relative could have had little idea what history had in store for its artist.

She said: "Anna used to go every year for a tourist trip to Austria and Germany.

"She was a great lover of travelling and carried out the same sight-seeing visits every year from 1894 until 1914.

"As I understand it she always used to bring something back for the family.

"Obviously one year she had been taken by this painting and bought it and brought it back here."

The five by three inch painting bears the hated Fuhrer's instantly-recognisable signature and its subject matter correspond with Hitler's activities the year it was painted.