If it's a one off it could be something serious, that can't be conveyed by email, so I'd go.
The last school I worked at we had to attend key stage meetings every Thursday lunchtime, with SLT 'presiding' over to share the outcomes or discussions they'd had at their SLT meeting on Wednesday. Mtg started at 12.15 (children went to lunch at 12.10) and usually lasted around 30 minutes, sometimes more. Lunch ended at 12.55...so we had to eat during the mtg and had no time to prep for the afternoon. It was just awful! Weekly staff meetings lasted 90 minutes (3.30 to 5pm).
We also had half termly 'school development meetings' which STARTED at 5.30 to give time for various Governors to get there...these were in addition to the weekly staff meetings, so that week was an absolute killer!
Every teacher HAD to run a club from 3.15 to 4.30 every week...it wasn't optional! We were told that we were not being reasonable if we refused.
I know technically we could have kicked up a fuss, but honestly, your life was made hell on Earth if you even hinted at union guidelines etc. I was working in excess of 75 hours a week...it very nearly destroyed me.
I'm so very glad that I now work at a school where staff wellbeing is paramount. Staff meetings last around 45 minutes...this week it was 30 minutes! No one is forced to do a club and they only last for 45 minutes if we do run one, 3.15 to 4pm.
Best thing I ever did, leaving that place!