When I was an electrician apprentice in the 1950s in the coal
mines in Scotland, I had to learn all other trades for one month
each one, before I got to our chosen profession, so I was
required to be a member of the union for each trade involved.
I had was in about 14 or 15 unions, as an apprentice I had
to pay between 1 penny and 3 pennies each week.
As soon as I could, I left for the R.A.F. and only once afterwards
joined one union as it was required when I worked a Heathrow
Airport.
Mike.