Eighty years after it was borrowed - and then never returned - an anonymous library borrower has quietly returned a 'lost' book containing rare photographs of the International Catholic Eucharistic Congress held in Dublin in 1932.

In an unexpected development that may relieve the nameless returner, the library has waived the late fees of over $5,144.

The book, a pictorial record of the famous Catholic Eucharistic Congress held in the first decade of the Irish Republic, was originally borrowed from the library in Navan, County Meath in December 1932, just a few months after the event itself took place. The borrower never returned the book however, and the library lost all record of the borrower or any of their details.

So staff at the library were astounded to discover the rare book in the returns pile on Monday, discreetly placed between other books left back on Saturday evening.

According to the Journal.ie, Meath county librarian Ciaran Mangan, who made the discovery, said that the return of the book was 'a very unusual occorance.'

Mangan said he was 'really intrigued' to discover who had held a copy of the book for eighty years. Mangan added that the return now is particularly timely, since the Eucharistic Congress will return to Dublin in two weeks time.

'We’re going to be very kind,' Mangan laughed, but he added that the book would not be lent out to borrowers in future. Instead it will remain in the library’s reference collection where anyone – including the person who secretly returned it – will be able to see it.

Mangan believes that it's possible and in fact probable that whoever originally withdrew the book is now deceased, which means it's most likely to have been returned by a surviving family member.

Mangan then asked for anyone involved in returning the book to contact the library via Twitter, Facebook or through the library’s blog.

Catholic Eucharistic Congress BookMeath County Library via Flickr