Mr Johnson, head of the 175,000- strong Union of Communication Workers, receives a salary of pounds 52,666, but his whole package is worth pounds 72,570 a year, including a particularly generous pension contribution by his employers of pounds 18,433. That compares with average pay of pounds 14,000 a year for Royal Mail delivery staff.
The UCW is one of two large unions to have submitted information on the earnings of its senior officials to the Government's certification officer under last year's Trade Union Reform and Employment Rights Act. The other union to have responded is the GPMU print union, which has disclosed the pay and benefits of Tony Dubbins, general secretary, at pounds 41,891.
In terms of basic pay, however, the nurses' leader Christine Hancock will probably emerge on top when all the figures are collated. Ms Hancock, leader of the 300,000- strong Royal College of Nursing, receives pounds 70,584 a year, beating Doug McAvoy, general secretary of the National Union of Teachers, whose salary is set at pounds 67,000 including a London allowance. Mr McAvoy, however, receives an employer's pension contribution of approximately pounds 4,000.
Unions will have to reveal the information five months after their financial year closes, which in most cases expires in June.
Apart from remuneration, some union leaders have been accused of drawing 'over-generous' expenses. For instance, Mr McAvoy's aides deny suggestions in tabloid newspapers that he has a luxurious lifestyle financed by the union. He is allowed second class train fare, an upper limit of pounds 45 a night for hotel costs, pounds 4.50 for lunch and pounds 13 for dinner, NUT officials say.
The public service union Unison, created by the merger between Nalgo, Nupe and the health union Cohse, is trying to work out a new salary scale that could give some senior officials, such as Rodney Bickerstaffe and Tom Sawyer, double figure percentage increases.
Mr Bickerstaffe, ex-leader of Nupe, and Mr Sawyer, who was his deputy, were the poor relations in terms of pay. Alan Jinkinson, general secretary of Unison and ex- leader of Nalgo, is understood to be on a basic of pounds 60,000 - which is related to the pay of a chief executive of a large local authority.
In terms of the ratio of basic salary to union membership, Bill Morris, leader of the Transport and General, probably comes out 'best value', at pounds 48,000 with a responsibility for 950,000 largely blue-collar workers. The worst in such terms is thought to be Arthur Scargill, whose earnings are estimated to be between pounds 50,000 and pounds 67,500, but who now has only about 8,000 members in the National Union of Mineworkers.
Garfield Davies, the recently re- elected leader of the shopworkers' union, Usdaw, receives a salary to which none of his members could aspire. Mr Davies draws pounds 50,844 a year, while his members' wages are among the lowest in Britain.
Conversely, the pay of Chris Darke, the pounds 46,350-a-year leader of BALPA, the pilots' association, is comprehensively beaten by the average salary among his members, which stands at about pounds 85,000.
Among the other 'big hitters' in terms of pay are Roger Lyons, pounds 58,300-a-year leader of Manufacturing Science Finance; Bill Brett, general secretary of the civil service union IPMS, on pounds 56,000; and Simon Petch, of the Society of Telecom Engineers, who earns a basic pounds 54,000.
Some trade unionists, seen as moderate by the Government, can enhance their life-styles through appointment to quangos. Bill Jordan, pounds 35,000-a-year president of the Amalgamated Engineering and Electrical Union, for instance, retains seats on various training bodies and is a governor of the BBC.
Most of the big unions provide chauffeur-driven cars for their general secretaries. Mr Morris has the use of a top-of-the-range Rover, while John Edmonds, pounds 52,000-a- year head of the GMB, the second biggest general union, is driven in a Ford Granada. Some union leaders can also command fees from newspapers for signed articles and in the past some have even acted as consultants to private companies.
A few senior officials depart with a golden handshake. Clive Jenkins, for instance, left Manufacturing Science Finance with more than pounds 200,000.