reportyourlevel says
If you file a VFR FPL then the aerodrome of departure will send a signal (called a DEP) to the destination to tell them your airborne time. The destination will take overdue action (starting with phone calls to relevant ATC units, ending with launching SAR assets) at ATD+EET+30mins. So half an hour after your estimate for the destination they will start looking for you if you haven't showed up. this will not happen without the FPL.
This is how I always thought the system would work, hence I always filed VFR FPLs, safe in the knowledge.... But reading the posts, it seems, in reality, this is rather hit-or-miss in the UK (and mostly "miss"). The destination is under no obligation to do anything. They may make some phone calls, they may not. The may not even have read the FPL (and thereby know what EET should have been, etc). This confusion/uncertainty is why I started this thread...and it seems to have come full circle (!). It seems there is big gap between what we would like to happen, and what would actually happen in a given situation. This is why I am mildly shocked. I thought this would all be "solid"...
(you get the impression of solidity when you're learning to fly and learning about FPLs -- all sounds excellent in theory...but sort of pointless if it doesn't actually work).