Born in Mill Hill, Cogger was educated at Willesden Technical College, before finding work with British Rail.
He worked as a box-boy, then a train recorder, before qualifying as a rail signaller.
He joined the National Union of Railwaymen (NUR), becoming active in his local branch, then secretary of the signallers' grade committee.
He was elected to the union's executive in 1974, and from 1980 was chair of the national negotiating committee.
However, under the union's rules, he could not serve consecutive terms as president, so left the post in 1992.