I've been trying to find out what 'intervene' means and have found these points on legal sites, though I'm no expert...
In recent years, UK courts have begun to allow third party interventions, to:
- Intervene in the public interest
- Raise some issue of public importance.
- Provide an independent analysis of the human rights principles and standards
- Enable the courts to hear arguments which are of wider import than the concerns of the particular parties to the case
- Help when the courts are to decide questions of major public importance, with implications going beyond the facts of the case at hand
TGtrd say "the judge in this case has given Transgender Trend permission to intervene in support of Keira Bell"... some legal sites say that third party intervenors don’t act for the plaintiff or defendant, but offer guidance to the court directly. Wonder if there will be other third party intervenors involved in the case too.
justice.org.uk/our-work/third-party-interventions/