Changes to Council Directive 85/3/EEC of 19 December 1984 on the weights, dimensions and certain other technical characteristics of certain road vehicles
EU Directive 1985/3
Made by Council Directive 91/60/EEC of 4 February 1991 amending, with a view to fixing certain maximum authorized dimensions for road trains, Directive 85/3/EEC
From legislation.gov.uk's record of changes, the official one: see it there.