The German judicial system should be in the dock for failing to bring Nazi war criminals to justice for so long, according to a Jewish history specialist.

History professor Dr David Cesarani was speaking after a German court convicted a 94-year-old former guard at the Nazi death camp at Auschwitz of being an accessory to the murder of at least 300,000 Jews.

Oskar Groening, known as the "bookkeeper of Auschwitz", was sentenced to four years in prison.

“Age, keeping your head down is not going to get you off the hook if you’re involved with genocide,” said Dr Cesarani.

“But sending a 94-year-old man to jail for four years does seem rather cruel.”

He said the sentence was roughly one year for 100,000 lives – and on that basis no sentence could really deliver justice.

“Groening was investigated in the 1970s – why did it take until now to put this man on trial and find him guilty?”

bbc.co.uk