History. 4 of 7: four unions called a vote within a month of their threat.
Hunch. ASCL itself chose to survey members first and only if nothing changes, with no dates.
The ASCL market resolves on ASCL news: YES if ASCL announces or opens a test or formal vote on action by 9 November, and NO if it only surveys members. BBC News and The Guardian are the backup.
We looked for cases where a UK union of senior staff who rarely strike, mostly head teachers, publicly threatened action against the government or a regulator. We found seven since 2009: five at NAHT, one at ASCL and one at the FDA, the union for senior civil servants.