A second wave would be inevitable with the current levels of positive tests and without an extremely robust test and trace system in place. It should not be forgotten that every infection in every country started from a single infected person, or a very small number of infected people. So if you open up and there is a single person capable of infecting others you have a second wave on your hands unless you can detect, trace and isolate everyone who is a carrier. No amount of optimism gets round that. "Lock down" is an attempt to starve the virus out of existence, so opening before you have ensured that you can detect any reoccurrence even in asymptomatic carriers rapidly and effectively is extremely short sighted.