Files from Bletchley Park, the UK's wartime code-breaking headquarters, are to be digitised and put online in a large-scale project expected to take up to five years to complete.

Undercover mathematicians and military operatives produced high-level intelligence at the Milton Keynes base during the war, providing crucial assistance to the Allied effort.

The work of the Bletchley Park staff, which included cracking supposedly unbreakable German codes generated by the Enigma and Lorenz machines, has been credited with curtailing the length of the war by up to two years.

The Bletchley archive currently exists entirely in paper format and much of it is difficult to view, making it inaccessible to the general public. Until now, only limited access to the archive has been granted to academics and educators under strict supervision.

Following an initial digitisation phase lasting around a year the documents, including communication transcripts, memoranda and photographs, will be made available for access using a combination of paid-for and free content.

The project is the result of a collaboration between Hewlett Packard (HP) and the Bletchley Park Trust, which runs Bletchley Park's National Codes Centre and its museum and educational facilities.

Simon Greenish, director of Bletchley Park Trust, said: "This will help preserve and considerably increase access to the historic fragile materials, as well as enable researchers to see and study documents from the code-breaking work that took place during World War Two. There can be few archives which contain material that had such a profound impact on the world at the time and which is still relevant today."

Norman Richardson, vice president and general manager of HP Imaging and Printing Group UK, said: "The Bletchley Park archive contains hundreds of thousands of documents tracing some of the most significant historical milestones of the 20th century, including some of the events that defined the outcome of World War Two.

"Our collaboration with Bletchley Park will not only ensure the preservation of this hugely significant archive but will also allow it to be made accessible and searchable digitally for the first time, untapping the value of this content for the benefit of audiences all over the world. We are hugely proud to be working with Bletchley Park and its team of volunteers to make this exciting project a reality."