The Bais Din of England ruled that it was permissible for the Chief Rabbi to attend out of respect for an invitation from the King. The leaders of every faith attended and they didn’t have to participate in the prayers, as far as I know, other than a joint declaration for the King by all of the faith lead leaders.
UJM,Avaira et al, please don’t be upset he didn’t ask your opinions.
Zetruth: what state of emergency?