Originally Posted by
bluemoon68
When you return to the UK and hand in your Passenger Locator Form, the authorities can see if you left the UK after the lockdown came into force.
I don't know if the information appears on the screen when they scan your passport or if it requires a bit more digging, but they don't need a PLF to know when you last departed the UK.
If you have several passports with different names that the system hasn't linked, you might "get away" with it but you could also "get away" with lying on the PLF if nobody reads it