This means you would have to clear security again though. How much time do you have?
What does the word "again" mean?
Flying SIN-ZRH-LHR, the pax has to go through security at least once. Or is SIN considered to be clean now?
Going from non-clean airside (non-Schengen) to landside and then clean airside (non-Schengen) involves one security check.
Going from non-clean airside (non-Schengen) to clean airside (non-Schengen) involves one security check.