A 91-year-old woman has been questioned by police in Germany — after she filled in the blanks in a piece of modern art based on a crossword puzzle.

The pensioner, who has not been named under German privacy law, was questioned under caution after she filled in the work valued at €80,000 (£67,000) with a biro.

"Reading-work-piece", a 1977 work by Arthur Köpcke of the Fluxus movement, essentially looks like an empty crossword puzzle.

Next to the work is a sign which reads: “Insert words”.

The hapless pensioner explained to police that she was simply following the instructions.

“The lady told us she had taken the notes as an invitation to complete the crossword,” a police spokesman said.