In his last story on the least important mutant book he created, Chris Claremont has Mesmero hypnotizing British Prime Minister Margaret Thatcher. I think Claremont put it in to remind everyone that this book takes place in Britain. Because Captain Britain wasn’t enough of a signal.
Anyway, from there the Fenris twins force Mesmero to help them infiltrate the Excalibur team, via Kitty Pryde, who is at a “finishing school.”
Eventually, it all gets figured out and there’s a big fight.
It’s really weird and pointless.