The ICL7502 was a remote job entry terminal from ICL which Hamish Dewar somehow managed to turn into a real computer.  There was a HAL cross-assembler which targeted this system, and a screen-based version of ECCE.  Although we have not yet found the source of the OS, we did find the source of the [http://history.dcs.ed.ac.uk/archive/staging-area/dectapes/153/iopack runtime I/O library], and the [http://history.dcs.ed.ac.uk/archive/staging-area/dectapes/153/solo Towers of Hanoi] program.