1955: Lead banned from petrol in Russian cities.
1967: Professor Derek Bryce-Smith organises conference.
1969: Banned in the US.
1981: Lead cut by two-thirds.
1982: Clear launched.
1986: Unleaded two-star petrol introduced in Britain.
1988: Unleaded petrol cheaper than four-star.
1992: EU says new cars must have cat converters and run on unleaded petrol.
October 1999: Lead-replacement four-star introduced.
1 January 2000: Leaded petrol banned.