This. According to all the available data, the median incubation period for SARS-CoV-2 is 4 to 6 days but it can take up to 14 days. That, coupled with the well-established risk of asymptomatic transmission, is the reason for a 14-day isolation period.
I've just come back from Spain, spent 4 days on a probably quarter full golf resort near Malaga. We only left the resort to go back to the airport on Sunday. I wore mask where I needed to, I washed my hands constantly, I maintained social distancing where I was told to - all the good things we were told to do, we did. The flights both ways were fine, full on the way there and about 3/4 full on the way back. At Malaga airport there were extra checks on where you were going, temperature checks etc, however nothing at Leeds Bradford, apart from the usual passport control. They didn't even check the government form you had to fill in to say where you were going to be staying for the next 14 days.
I don't regret going, I had a great time, and have fully accepted that I now need to quarantine for 14 days. However, I felt far safer being there than I have here in the last 4 months. The people over there have accepted the controls for what they are, everything is cleaned, and cleaned again, and everyone is wearing a mask all the time except if you are eating or drinking (or playing golf), everyone is washing their hands, everyone is staying 2m away from each other.
I think sitting in a tin can for 3 hours, twice, is the biggest risk, and the reason you need to self isolate for a fortnight, but if I had been contacted by a tracer, telling me that I had been near someone in Morrisons who has now tested positive, I therefore need to go and get a test immediately. If that test comes back negative then great, I can crack on, despite me possibly being infectious as I'm still within the 14 day period - but I am allowed to go outside and about my business. Can anyone explain how its any different from returning from Spain? (Which when we travelled we were told was fine to go to, and were encouraged to, to help get the economy and tourist industry back on its feet by the way).
It does sound like they might be changing the advice to 10 day quarantine, with a test on day 8, which makes even more of a mockery of the advice.