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The CTL Modular One was a computer developed in the 1960’s and 70’s in the UK by Computer Technology Ltd. A company founded by Dr. Iann Barron. It was used by universities, some hospitals, CERN, The European Space Agency and the National Physical Laboratory (NPL) where it was used to develop packet switching networks and the first networked word processor called ‘Scrapbook’. The NPL Network had an operating speed of 1.5 Mbps which was revolutionary for the time.  Details of the history can be found on the NPL website under Mathematics and Computing (see link below).

This Modular one was purchased from NPL in 1980 together with two teletypes and a high speed paper tape reader. There is one other known system at the Museum of  Science and Industry in Manchester.

Details of our system are in the following pdf documents;
 CTL Modular one                                    11 MB.
 System Equipment Catalogue                  31 MB.
 Software Paper Tapes                              0.4MB.
 Modular One Peripherals                        4.5MB. 
 Restoration Tasks                                  16.5 MB.
Right click the link to download (browsing may be slow).
(All WIP and subject to change).

Links to articles related to the Modular One:
Wikipedia
NPL Mathematics and Computing
The Scrapbook project Video
The Packet Switching project Video
Roger Scantlebury  BBC Video
University of Birmingham History
Interview with Donald Davies (referred as Modula-1 here)
CERN justification for purchase of the Modular One
Sydney Brenner, Modular One: First computer in the Lab
The National Museum of Computing NPL Internet Gallery
The Origins of SpaceWire
Search instructions for Modular one at the Museum of Science and Industry Manchester