My son has just moved into a flat which has a boiler which I presume
from his reports is a combi - no storage tank AFAIAA. There is a
pressure gauge which is currently reading well into the red. Apparently
the heating and probably the hot water are switched off. Is this a
problem, how could he release some pressure if necessary and is there
any danger in turning it all on? Sorry if these are basic questions but
I have only ever had stored water systems myself. TIA.

Peter.