Hi all.
This sounds a weird one to me. In the bathroom of my daughter's flat
there is a toilet, sink, and bath. The bath has mixer taps and a
flexible hose to a shower head. Cold water is mains fed. Hot water is
from a water tank at mains pressure.
Everything works, but...
When you turn the shower head on, after several seconds water starts
dripping/running into the toilet bowl. I've only tested this briefly
using the cold water to the shower head. Running the sink or bath taps
does not cause this to happen.
What's the cause?

The toilet cistern is ceramic with a dual push button thing on the top.
If I try to lift the cistern lid, I am stopped by the mechanism attached
to these buttons. How do I remove the lid?

Ta.