Does lockdown work without checks at UK airports?

"Not a single person at this airport has asked me anything"

The United Kingdom has been on lockdown for more than a week, with gatherings of people also prohibited under the government's plans to slow the spread of COVID-19. These measures were relatively late, coming after it became clear that the original plan for the UK to acquire 'herd immunity' was misguided at best. While staying at home and minimising your contact with other people undoubtedly works, is it possible that this policy is being handicapped by gaps in the response elsewhere? Comedian Tez Ilyas recently returned to the UK from a trip to Australia via Abu Dhabi, and disembarked his flight expecting to be checked and questioned about where he had travelled. To his shock, that did not happen. He exited the flight, walked through the airport as he normally would and returned to life as normal... or as normal as life is right now. Before he left however, he recorded a video from the airport illustrating the lack of checks arriving passengers are being subjected to, and asks what good is lockdown if the UK won't screen people flying in from overseas. https://twitter.com/JOE_co_uk/status/1245364886391140358?s=20