From LUL travel news today. "Severe delays on the Metropolitain,
Circle and H&C line due to a faulty train at Finchley Road"

I can understand why a faulty train a Finchley Road would cause sever
delays to the Metropolitain line, but why would it cause severe delays
on the Circle and H&C line? Surely, if anything, there would be fewer
delays on these lines as there would be no pesky Metropolitain line
trains in the way?