Hat tip Jonathan Dunning via Adrian Kennett. One of the worse things about being a trade union rep is that non members will contact you about serious issues and ask for representation. In the same way that you cannot get car insurance, after you have crashed your car, this can't happen. You have to say no. Unions would go bust if workers only joined when they had a problem.
While locally in my employer, Reps have agreed to allow someone to join with a pre-existing issue and get limited verbal advice (if they had not previously been asked and refused to join). They will not get physical representation at discipline, sickness, grievance or redundancy meetings nor access to full time officials or our union solicitors.
Ironically, it tends to be people, who when I asked why they had not joined previously, say that they didn't because they really trusted the employer so much and never thought they would be treated in such a way.
As a trade union rep for over 30 years, I can say without a shadow of a doubt, that it can be amongst the most frightening and stressful experiences of your life, to try and deal with a serious employment issue by yourself.
So if you work in any organisation that provides public services (NHS, Local Government, Police or Justice staff, Utilities, FE/HE, voluntary, charities, housing associations, 3rd sector or private employers who provide public services) then join via https://joining.unison.org.uk/join-unison-today/
If you work for another employer, check out this TUC website "Union finder" to see who you should join https://www.tuc.org.uk/join-a-union