With privatisation looming, the 67,000-strong Rail, Maritime and Transport workers' union is demanding a guarantee that there be no compulsory redundancies and that contractors are not brought in to undertake work normally performed by BR employees.
Both sides agree that an assurance over compulsory redundancies is within reach, but the second problem is more intractable.
When the union talks of a 'guarantee of no compulsory redundancy' it is adopting a firm public position which, in private, may be open to negotiation. When BR says the union is demanding a guarantee of 'jobs for life' it is adopting a similar tactic. Senior officials at the RMT concede privately that a copper-bottomed guarantee that no one will ever be forced out of the industry through redundancy is not achievable and probably not deliverable by BR. They are looking for a 'form of words' which would make such an eventuality highly unlikely and have given examples to BR of industries where such deals exist. Management believes a form of words on the issue to satisfy both sides is achievable.
The second element of the dispute - the threat that contractors will take over the jobs of BR employees - strikes at the heart of the union's fears over privatisation.
Management has said that it will endeavour to avoid compulsory redundancies because of 'contractorisation' and that displaced workers will be offered other jobs. It has refused, however, to guarantee that the use of contractors will not be extended and the union is unhappy with the fact that a London employee might be offered work in Inverness or Newcastle.
BR's hands are tied to an extent by the Government. One of the most worrying developments, as far as RMT is concerned, is the establishment of Railtrack, the free-standing organisation which ministers have ordained will take over ownership of track and signalling. It will initially employ existing BR employees, but after an unspecified time it will call for bids from contractors.
Jimmy Knapp, the RMT leader, sees a future in which railworkers have little job security, RMT will become marginalised and employees will have no union protection. Thus it is difficult to disentangle the political background from the legitimate industrial concerns. It is also why in a brief but bitter encounter on Wednesday night Sir Bob Reid, BR chairman, accused Mr Knapp of harbouring a 'political agenda'.
BR's dispute with the 16,000-strong train drivers' union Aslef, which will also be out on strike today, seemed to move nearer resolution last night.
Derrick Fullick, general secretary of Aslef, is worried that his members' employment conditions and their job security will change when they are transferred to 'shadow franchises'.
Senior BR negotiators have offered Aslef a guarantee that they will be involved in talks to set up the new organisations. Management last night was confident that fresh talks on Monday could resolve the dispute with Aslef.