Strikes need a lot more votes than Conservative leadership elections

The law governing votes for industrial action has been in the news lately for obvious reasons.

In short, at least 50% of eligible members of a trade union must have voted in a ballot for industrial action to be lawful. 

In England, there is a further requirement governing ballots in important public services, such as education, which is that at least 40% of all eligible members (not only those who voted) must be in favour of industrial action.

As trade unions may have tens of thousands, or hundreds of thousands of members, and ballots have to be conducted by post, this is a high bar.