Great thread - many of the non medical issues listed above such as cost and being turned away at the airport are probably more relevant than the science.
No test that is only 60% effective is going to cut the mustard. The PCR is getting quicker and cheaper but although 97% eficacious, that depends on getting virus on the swab - even a trained healthcare worker fails in 20% of cases. The false positive is only 1% but this applies to the entire population, so if you tested just at Heathrow, 800,000 a year would be falsely stopped at the terminal.
We can calculate the efficacy of a combination of PCR swab plus isolation plus testing for symptoms - this is what we do in the UK for hospital admissions. 7 days isolation and a negative swab and no symptoms misses only 1 in 130,000 cases and so can be said to protect the border, but the swab has to be done after 3-4 days, not on arrival
Personally I believe we will have a vaccine within weeks and I worry the politicians are mucking around. The initial vaccines have been bought and are being manufactured but will need to be stored very cold. Now is the time to organise this and plan to get the vaccine to every high street so it can be rolled out in days. Serco and the army are no better at vaccinating than track and tracing !