Woodfield Mill in North Yorkshire is one of the photos on the site

More than 20,000 previously unseen images have been made public on the website ViewFinder.

It is aimed at the history enthusiasts, schools, the public and specialists, and was made possible through a grant of �170,000.

The archive was unveiled in Swindon on Thursday by English Heritage Chairman, Sir Neil Cossons.

He said: "These are our grandparents and great grand-parents at work, it is a record of who we were and it informs who we are."

Sir Neil added that English Heritage's long-term goal was to digitise most of its 10m archived photos.

These are normally only accessible at the public search rooms of the National Monuments Record in Swindon and London.