If in doubt, go back all the way but putting the most recent jobs first and, if necessary, simply summarising the earliest employment.
e.g. start with "2011 to present: Deputy Controller of thingummy production at Bloggs and Whatsit Ltd, with special responsibility for staff development within the widgets section and oversight of health and safety policies throughout the company"
but end with
"1980 to 1991: Lathe operator, producing widgets and whatsisnames, at Slavedriver plc, then at Hardgrafter Ltd and Brownoser Developments Inc".