Modern Records Centre, University of Warwick

The Modern Records Centre (MRC) is the specialist archive service of the University of Warwick in Coventry, England, located adjacent to the Central Campus Library. It was established in October 1973 and holds the world's largest archive collection on British industrial relations, as well as archives relating to many other aspects of British social, political and economic history.

More information, including a list of holdings, on the Wikipedia page.

The website is.