It began on a table in the Scottish Poetry Library with an old book, some paper and a carefully crafted note.

Only one person knew how long it had lain there but they weren't telling. It was a secret, its maker unknown. That was part of what made it beautiful.

It was a tree, intricately fashioned from paper pages into branches and leaves, rooted on a thick leather-bound old book.

At the base of the tree was a fragile paper egg broken in half, the inside lined with gold, in which lay a collection of carefully hatched words.

Put together, they made a poem by Edwin Morgan - A Trace of Wings - and came with a note written with a meaning as delightful as the sculpture itself.

It was addressed to the library's Twitter account called By Leaves We Live, a Patrick Geddes quote about the idea that you reap what you sow.

The note read: "It started with your name @ByLeavesWeLive and became a tree... We know that a library is so much more than a building full of books... a book is so much more than pages full of words... This is for you in support of libraries, books, words, ideas..."

It was the first of many sculptures, right up until the most recent model unveiled for Book Week Scotland this month.

Julie Johnstone was the staff member who discovered the original that Wednesday morning in March 2011.

Along with her colleagues, they nicknamed the sculpture"poetree" and posted a thank you note online to their anonymous artist.

"We are lost for words to describe the intricacy and care that has gone into it," they said.

"We are lost for words to thank you for giving us such a beautiful thing."

Despite national publicity, the identity of its maker remained unknown.

Then three months later, it happened again. This time, two sculptures came along almost back to back.

Since then, a whole collection of sculptures have popped up in surprising places.

Over the last five years, the artist has become a sort of Banksy of literature, with more delicate sculptures popping up in various locations connected with the written word, such as museums and libraries.

Usually cut from the pages of a book, models have been left at the Filmhouse Cinema and the National Library of Scotland in Edinburgh.

The Filmhouse creation was a delicate model of a cinema, with a tiny paper figure of bestselling Scottish author Ian Rankin included.

He was portrayed perched in the audience drinking a bottle of Deuchars with warriors on horseback leaping from the screen.

A note left with it read "For @filmhouse - a gift - In support of Libraries, Books, Words, Ideas ... & All things *magic*".

The National Library, meanwhile, received a model of a coffin and a gramophone sculpted from a copy of Rankin's novel Exit Music.

The note accompanying the sculpture read: "For @natlibscot - A gift in support of libraries, books, words, ideas..... (& against their exit)".

Ian Rankin denied it was him and the mystery has always continued.

Amongst the creations found, mostly during 2011, have been a dragon's nest, a magnifying glass and a teacup.

The sculptures and the mystery over the identity of their creator, made local, national and even international news.

To this day, the identity of the talented creator has still not been revealed, though in 2012, a small clue to their origin was revealed in a book published on the collection.

In it, the sculptor wrote that at the heart of the project was: "A woman, who had been a girl, whose life would have been less rich had she been unable to wander freely into libraries, art galleries and museums. A woman who, now all grown, still wants access to these places and yes, wants them for her children..."

A collection of ten Edinburgh sculptures were brought together in December 2011 for a one-night private exhibition at the Scottish Parliament.

The following year, they were sent on a small 'mini tour' of Scotland and by the winter, the mysterious artist announced that five more sculptures that were to be hidden around the country to mark Book Week Scotland.

Then, in 2014, during a tour of another work made from intricate paper butterflies, the artist offered to collaborate with members of the public who sent in their own paper butterflies.

A few months later, the sculpture dropped a hint in an email interview with the BBC, that more sculptures were to come, saying "What makes you think Butterflies is my most recent sculpture?"

Then, in March 2015, the artist announced the time had come "to draw time on the project".

A request was made for the public to make their own butterflies before a given deadline which would then be made into a final sculpture.

Butterflies flew in from all over the world and from all different age groups of contributors and in August this year, it was finally unveiled at the Edinburgh International Book Festival.

Poetically, it began and ended with a tree.

The Butterfly Tree and the Lost Child featured a 2m tall paper tree, larger than the artist's first sculpture, accompanied by a small paper child holding a book, features butterfly-shaped leaves made by members of the public from as far afield as Spain, Greece and the US.

A hand-illustrated book was left with the sculpture, telling the fictional story of the Butterfly Tree and how it reached out and comforted the Lost Child.

The work has been donated to the Central Library, where it went on display this week to mark Book Week Scotland and the end of a five-year journey that captivated the imagination of thousands.

It will be kept their permanently on the windowsill of a staircase leading to the Reference Library so the fragile wings of the butterfly leaves can still be read.

The artist intends to remain unknown.