Art hoarder Cornelius Gurlitt made a Swiss museum the “sole heir” for the vast collection of Nazi-looted art he stored in his apartment over several decades, it has emerged.

Mr Gurlitt died on Tuesday aged 81 after undergoing major heart surgery.

His huge collection - worth an estimated £850 million - was confiscated by authorities in Munich in 2012, but was kept secret for almost two years until it was finally revealed by the German media last year.

The Bern Art Museum said it had no prior relationship with Mr Gurlitt and had had no idea that he would bequeath the collection to the museum.

“The Board of Trustees and directors are surprised and delighted, but at the same time do not wish to conceal the fact that this magnificent bequest brings with it a considerable burden of responsibility,” the museum said in a statement.

“It also brings a wealth of questions of the most difficult and sensitive kind, and questions in particular of a legal and ethical nature.”

Mr Gurlitt’s spokesman, Stephan Holzinger, said his client had no close relatives and wrote his will a few weeks before having a serious heart operation.

Mr Holzinger also cautioned against “wild speculation” saying that a court would decide whether the will was valid and legally binding.

The collection of more than 1,400 pieces, including works by Pierre-Auguste Renoir, Pablo Picasso, Marc Chagall, Emil Nolde and Max Liebermann, was only discovered after a routine customs check found Mr Gurlitt carrying huge sums of cash.

An additional 60 pieces belonging to Mr Gurlitt were found earlier this year in another house he owned in Salzburg, Austria.