Perhaps someone from the UK can explain, but i don't even understand how mermaids has the ability to try and use the court to revoke the charity status of a different organization. Courts in the US usually are obsessed about "standing". Basically the person bringing a case needs to prove they are harmed. The article here makes it appear that mermaids had no standing but the LGB alliance was still dragged through the courts.

I say the US courts "usually" care about standing because lately everything is being politicized and the SCOTUS just issued a ruling on student loans despite there being no standing. The claim of standing was on behalf of the student loan company which explicitly said it didn't want to be part of the case and somehow the court just allowed it. I guess standing is only an issue when the judges are ideologically opposed to the case.