After a two year gap I have just had the fourth tyre pressure alert on my car.
The first two were false warnings.
The third was genuine but I ignored it after the two false ones, and found a flat tyre next morning.
After the fourth one today, I checked the pressures and found one tyre 5psi down, and took it to a tyre place, who found a nail in the shoulder.
So this last warning the system did its job perfectly!
The journey was from the midlands to London and the warning came on as soon as I left the motorway and stopped at some lights. I guess the rotational speed difference was immediately more noticeable to the system at low speed.
Unfortunately The tyre place didn't have any Michelins so now I have three 37,000 miles Michelins, and one brand new Goodyear. Might replace the three Michelins with Goodyears when the time comes to get back to a matched set.