If it was due to disability/H&S then that would be fair grounds to refuse the training, as long as the employer is aware of the situation.
Maybe the business needs have changed, or the way that things work need to be updated and that is why they are requesting the training - the employer shouldn't need to justify it, IMHO any opportunities for training should be grabbed!
Just because the worker has done that job that way for 25 years, doesn't mean things shouldn't/can't change - unless there are valid reasons for not wanting/being able to undertake the training.
The employee is my dad. There is no reason he doesn't want to do the training, other than he is very shy and hates looking a prat when he gets things wrong. He just doesn't want to do it.
Career enhancement isn't really relevant, he only has a few years work left as he is already in his 60's.
Yesterday morning things took a change anyway. He went into work, they obviously mentioned either training or disciplinary and it escalated into an argument with him telling them they can stick their job and verbally gave four weeks notice.
The crux of it is, he is a stubborn old man and feels forced into doing something he doesn't want to do.
To be fair to him, he has been under a lot of stress the last two days, as on Wednesday my mother's wedding ring was stolen. but the refusal to do the test has been going on for a while, he just lost his rag because of his home being burgled. But he's a very private man, so won't have told anyone about it.