Any teacher will know if there is a pupil constantly seeking to go to the toilet,
How though?
Looking at my children's timetables, it would be very simple to work out a rota of lessons to ask to use toilet so as not to alert a given teacher to excessive use.
Unless there is some sort of database where teachers log toilet visits I'm not sure how any teachers would know who is leaving other teachers' lessons. The only sort of schools that would have this sort of system, I suspect, will be the RTL type schools who remove all the grey areas.
The notion that senior leaders are perma-free and omnipresent is, I would expect, unlikely. I know some SLs and their work load is immense.
Lastly, I've checked my childrens' timetables. They are never more than 55 minutes away from having an opportunity for a piss. At this point, given that some are proclaiming the right to ask to go to the loo (whether you need a pee or not) to be some sort of universal human right, do the teaching staff have this right? Can they just walk out of a lesson* leaving the class alone to their own devices for 5-10 minutes as they walk to find a staff toilet, use it, and return?
If not, why not. It's a human right, yes?
*I suspect a teacher leaving a class could be grounds for a charge of gross misconduct.